GIT

 GIT -> definition -> open source distributed version control system -> its main purpose is to track changes to files and directories in a project -> it is, however, a very powerful tool which provides features such as -> versioning, branching, forking and navigating between all of these -> allows multiple people to easily work on the same project without interference -> limited debugging -> easy repository integration -> enforcing a working flow -> much more :)								   -> it is used mostly in software development environments, to track changes to source code.   -> concept -> low level storage of data-> at its core, Git can be thought of as a table of -> KEYS -> the SHA1 hash of a VALUE it references												      -> a hash is a string which represents the content of an object, not the object itself    						     					      -> VALUES -> any sequence of bytes (file contents, directories etc)						     							-> the values are stored under these KEYS (are referenced by the keys)													-> each VALUE represens an OBJECT -> an object is a sequence of bytes, which is, a VALUE									  								  -> each object is referenced by a KEY, which is, a SHA1 hash								  									  -> if two objects are identical, Git will store only one and will use it everywhere it is referenced							          									  -> a file and its content is stored -> the content in a (is a) BLOB object and is the actual hashed value which gives the KEY -> the filename and permissions in the TREE object -> for example, if two files have the exact same content, the TREES where these files are, will reference the same BLOB (and not two identical blobs) -> three main types of objects -> BLOB -> it is the contents of a file, at some point in time, stored in Git -> it is the actual data -> TREE -> a directory stored in Git -> it has a list of hashes for each object it contains -> it contains filenames which point to blobs and another trees -> COMMITS -> is just a piece of text and nothing else -> Just git cat-file on the SHA of a commit -> points to a graph of trees and blobs that represent the project at the moment of that commit -> contains -> the commit metadata -> the hash of the parent commit -> It is missing if first commit -> this means that a commit also points to its parent commit, which is the previous commit where this 'current' commit originated from. -> the hash of the content of the root directory (tree) of the project -> TAGS -> are used as another way to reference a commit beside its hash -> two types -> SIMPLE TAG -> it is a pointer to the commit where it was created -> a reference to a commit, just like a branch -> it is a simple name, and nothing else. -> ANNOTATED TAG -> just like the simple tag, is a pointer to the commit where it was created -> it is the fourth type of object in Git -> it is made of two parts -> a pointer to the hash of a BLOB -> the BLOB which contains tag metadata and another hash, of the actual commit tagged -> works by moving data around four conceptual areas -> WORKING AREA -> the place where you keep the files and folders you are currently working on							 	                   -> it is the directory where you do the actual work (edits) -> INDEX-> the changes are moved here before a commit -> it is the area where changes from working directory are staged before commiting -> it specifically is the 'index' file in the .git repository -> while in its implementation it is supposed to be seen as a temporary transition area, index actually contains all the data, just like the repository -> the message 'nothing to commit, working tree clean' means that the index area contains the same files as the repository -> REPOSITORY -> contains all the history of the project -> commited changes go here -> stored in the .git folder -> structure -> .gitignore -> specifies which files are ignored by Git -> accepts regex patterns -> "ignores" means that git will never display the files as untracked or staged, and it won't track any changes to them -> .git\objects -> folder where Git stores all its objects. -> sort of an objects database -> first two hexa chars from the object's SHA1 hash will be the name of the subdirectory where the object is stored -> the rest of the hexa chars from the object's SHA1 hash will be the name of the file where the object is stored -> .git\info | -> used for optimization purposes -> .git\hooks | see CONCEPT -> layer of optimization -> .git\refs\ -> a folder where Git stores the files which contains references (like branches, tags, remotes) -> references are found all over Git, not only in this folder. For instance, each commit object references its parent. -> Git uses references between commits to track history and references from commits to trees and blobs to track content (the state of the project) -> HEAD -> is a reference that points -> usually to a branch, in which case HEAD points indirectly to a commit. -> rarely, directly to a commit (contains a hash) -> this is also called the 'detached HEAD' state. -> a detached HEAD is a commit which doesn't belong to any branch -> its purpose is to -> reflect the current commit. The commit that HEAD points to (either directly via hash or indirectly via a branch ref), is the current one. -> determine the parent of the next commit. The command git commit, creates a new commit object, whose parent is the commit which HEAD points to. -> tell you where you are. Since it points to the current commit, it is a good indicator to where in the project's history you are working. -> .git\refs\heads -> contains the branch references -> BRANCH -> is -> a pointer to a commit (directly, via SHA1 hash)							 | while the 'branch' term refers to the actual reference, the series of -> a series of commits, where each commit is linked to the previous one in a parent-child relationship. | commits that this reference points to is also called a 'branch' -> the branch ref points to the last (latest) commit in the series. -> BRANCHING -> a newly initialized repo has a single branch, called master or main. -> when a commit is made -> a new commit object is created which points at its parent -> the branch ref is moved along to point at the new commit, which implicitly moves HEAD to point at the new commit, which means that this new commit will be the parent of the next. -> this is how a series of linked commits (a branch) is created. -> if a new branch is created -> a new branch ref is created. -> the new branch ref points at the current commit -> at this point, the current commit has two branch refs pointing at it, the old branch, and the newly created one. -> the branch ref that HEAD points to (as example, the new branch ref) will be moved along at the next commit, and the next, and so on, creating a series of linked commits. -> switching to the old branch -> moves HEAD to point to the old branch ref -> commiting will move the old branch ref along with the new commits, creating another series of linked commits. -> at this point we have two separate series of linked commits, both of which share a common commit -> called the Ancestor Commit -> switching to a branch -> since HEAD points to the branch ref, the commit that the branch ref points to, is the current commit. -> switching the branch, makes HEAD point to another branch ref which, in turn, points to another commit. -> switching HEAD to another commit updates the INDEX and the WORKING AREA with the state described by the commit (see git checkout command). -> as each commit points to its parent, switching to a branch ref switches to a series of linked commits. Effectively, switches to a branch. -> .git\refs\tags -> contains the tags -> .git\refs\remotes -> contains subfolders for each remote, each containing the branches of that remote -> .git\config -> git config file -> .git\index -> a binary file -> contains a list of all files in the current branch,their checksums, timestamps and filenames -> it can be seen as as the file that stores what we need to commit. -> it is the same as the INDEX that we are talking about throughout this document -> STASH -> contains the stashed changes from index and working directory that is not yet commited -> can be though of as an area where the work can be saved for later, if somethin else needs to be done -> its content cannot be modified, other than using git stash directly. -> can contain multiple elements -> one element represents the all the changes stashed once -> each element has a serial ID and a commit hash to make it easier to identify -> for example -> a regular flow of data across the four areas when working with Git would look like: -> same version of files in WORKING AREA, INDEX and REPOSITORY -> modifications -> GIT ADD -> modifications added to the INDEX -> GIT COMMIT -> creates a new snapshot/version of the INDEX -> in depth explanation -> cloning a repository, or initiating one, would result in the same version of all files in WORKING DIRECTORY, INDEX and REPOSITORY -> it starts with a commited version of the index -> this is the version present in the repository -> working directory and the index have the same versions of the files -> changes are made to files (the version in the working directory) -> the changes are not permanent, they can be undone -> displayed with red text by "git status" -> changes that are final and deemed good are added to the tree (staged/added to the staging area) -> displayed with green text by git status -> changes still not permanent -> adding files to the staging area can be seen as preparing a "final" version of the index -> if the index is what we want, a commit is made -> that version of the index is made final with a commit (we are sure that's how we want the index to be) -> the changes are permanent "for now" representing a new version of the repository -> it is also called a snapshot -> this "final for now" version has been saved and we can revert to it																							    -> the local repository is updated with this version -> else, changes are reverted/deleted and we'll work towards a better result -> no need to use the Stashing functionality yet. -> commands -> most of the commands can be understood logically by asnwering TWO QUESTIONS -> how does this command move information across the four conceptual areas described above? -> how does this command change the Repository? -> NOTE -> the commands below and their functions are described, first, from a conceptual point of view (what it is supposed to do in Git). -> However, the -2Q> describes their actual actions from the perspective of the two questions, for a better understanding (I hope) -> GIT INIT -> starts tracking the changes in a folder by initializing a new git repository. -> effectively creates a new git project (called a repository) -> creates the .git HIDDEN FOLDER -> contains all the necessary tools to track the project -> contains the whole repository -> this is the folder copied from a remote source when cloning -> OPTIONS -> --bare -> GIT CLONE ['uri'] -> clones a remote repository -> when cloning, only the main branch is copied (everything it has, including the log), and it is set to track the main (master) branch of the remote repo -> the other branches will be copied locally afterwards, if wished so		                     -> when a repo is cloned, Git automatically adds a remote relationship with the original remote repo, called "origin" -> OPTIONS -> --bare -> GIT ADD ['file'] -> adds the files (untracked) or modifications (tracked), from the WORKING AREA, to the INDEX -> when a commit is made, the current form of the INDEX is saved (snapshot) and the local REPOSITORY is updated -> also known as the STAGING AREA -2Q> copies the updated file(s) from the WORKING DIRECTORY, to the INDEX, overwriting the previous ones (if applicable). -> OPTIONS -> -n / --dry-run -> do not perform the ADD operation, just show what files would be ADDED -> -v -> verbose -> -u -> stages all updated files, but not untracked files -> -A -> stages all files including both untracked files and updated files -> GIT COMMIT -> commits the changes from the INDEX, to the REPOSITORY -> each commit creates a new snapshot (version) of the repository -2Q> copies the files from the index to the repository -2Q> creates a new commit object in the database -2Q> creates another objects -2Q> updates the current branch (moved the pointer) -> OPTIONS -> -a -> automatically stages all modifications, effectively skipping the staging area step -> -m "message" -> adds a message to the commit, without opening the editor -> if -m is not used, Git commit opens the default editor so a commit message can be wrote. After this, it will commit to the staged modifications. -> --amend --author [User Name ] -> allows changing the author of the last commit -> GIT CLEAN -> cleans the working directory -> OPTIONS -> -n -> shows what would happen if the command is issued, without making any modifications -> -f -> performs the clean -> GIT STATUS -> shows the modifications from the working tree (working directory), not yet commited to the repository (modifications to the tracked files, or adding new, untracked files) -> shows only for the current branch -> shows if in detached HEAD state -> shows if the current branch is in sync with the ORIGIN repo branch -> OPTIONS -> -s / --short -> shows a shortened version of output -> "M" (modified) is a modified file, which may be staged or not. "??" (unknown) is an unstaged untracked file. "A" (added) is a staged untracked file -> GIT LOG -> shows the history of the repository on current branch -> the first commits displayed are the latest (reverse chronological order) -> OPTIONS -> -1 -> any number -> limits the number of commits displayed -> --oneline -> shows the commits in a one line shortened version -> displays the first digits of the SHA-1 hash, refs and commit message -> --stat -> shows more details about the modifications in each commit -> --patch -> shows the full diff for each commit -> --all -> shows for all branches -> --decorate -> shows tags and any other notations -> --graph -> provides a graph of repository's evolution -> when --graph is used, most commonly the following options are also used for better formatting: --all, --decorate, --oneline -> Example: git log --graph --all --decorate --oneline -> GIT REFLOG -> records when the tips of branches and other references were updated -> provides a more detailed log -> GIT SHORTLOG -> provides a summarized version of the logs "suitable for release announcements" -> with no options, basically lists the authors and their commits on a branch -> OPTIONS -> -s -> summarizes the output by showing only the authors and the number of commits -> -n -> sorts the output based on the number of commits per author -> -e -> shows the author's email -> GIT SHOW [commit | file] -> shows the commit whose SHA is provided just as displayed by "git log", or shows the file whose hash is passed as argument -> GIT STASH -> stashes the working directory and staging area as WIP and clears the working directory -2Q> two actions -> copies all the changes from WORKING AREA and INDEX that are not yet commited, in the STASH area -> checksout the current commit (clearing the INDEX and the WORKING AREA) -> OPTIONS -> save -> the default option -> git stash = git stash save -> list -> lists the contents of the stash -> show -> shows a more detailed view of what files have been stashed -> pop -> returns the stashed changes in the working directory/index and removes them from stash -> apply [element] -> reapplies the stashed changes of the element supplied, to the working directory/index while also keeping them in stash -> if no element is supplied, applies the most recently stashed changes -> an element is a set of changes from the WORKING AREA and INDEX, stashed once using git stash save. -> drop -> removes the last stashed changes -> clear -> clears the stash -> branch [branchname] -> creates a new branch and applies the stashed changes to it					 -> --include-untracked -> stashes untracked files -> GIT DIFF -> with no arguments or options, shows the differences between the WORKING AREA and the INDEX -> [commit] -> with one argument, shows the differences between the specified commit and the current working directory -> the commit is specified either by its SHA hash or using HEAD -> HEAD = last commit -> HEAD~1 = one commit back (1 = number of commits back) -> [commit] [commit] -> shows the differences between two commits -> [commit][commit][file] would list the differences related to the supplied file between the supplied commits -> [commitA]...[commitB] -> shows the differences between the common-ancestor-commit of commitA and commitB and commitB -> useful in the context of branches -> it is useful to display the differences between the master as it was when the feature was created, and feature as it is now -> it is equivalent to $git diff ($git merge-base [commitA][commitB]) commitB -> the difference between git diff and three-dots-git-diff is -> git diff -> shows all the differences between branches 3-dots-git-diff -> shows just the differences between the common-ancestor of the two branches (master and feature for example) and feature just as if the master branch had never moved forward -> the name of a branch passed as argument equals to the HEAD commit in that branch -> commits can be identified by their hexadecimal strings of characters ids -> output -> diff --git a/test.py b/test.py	   | diff --git marks the beginning of a new comparison. Next, are the compared files, called a and b and then names of the actual files index 30f664c..5447a65 100644	   | files metadata (file hashes, mode identifier) --- a/test.py			   | --- and +++ are file markers. They are used to identify which lines belong to which file +++ b/test.py			   | /dev/null				   | file marker when the file is new or deleted @@ -423,4 +423,4 @@ def step6(self):   | where the changes occured. -423,4 means showing 4 lines (,4 -> for context) beginning with line 423 return True			   | |					   # this line is added for test 	    | -# hello 2				   | - line represents a line from file a which is different from the same line in file b					    \ No newline at end of file		    | when there are lines displayed without - or + it means that line is identical in both files +# hello 23				   | + line represents a line from file b which is different from the same line in file a					    \ No newline at end of file		    | -> git tracks file contents using hashes of their contents. If two files have the same content hashes, git might interpret that as a file rename. In this case --no-renames should be used. -> OPTIONS -> --staged / --cached -> shows the differences between the INDEX and the REPOSITORY -> --no-renames -> turns off rename detection -> HEAD -> shows the differences between the working directory and the HEAD commit in the same branch, effectively showing all staged and unstaged changes -> -w -> ignores whitespace changes -> GIT CHECKOUT [commit | branch | file] -> definition -> "Switch branches or restore working tree files" -> "Updates files in the WORKING TREE to match the version in the INDEX or the specified tree" -> the most common uses of this command is to switch to a branch or restore file(s) to their commited state. -2Q> if a commit is specified (hash/branch) -> moves the HEAD ref to point to the specified ref (either by branch or SHA), in the repository, essentially changing the current commit -> copies the current data from the REPOSITORY to the INDEX and WORKING AREA -2Q> if a commit is not specified -> copies the data from the INDEX to the WORKING AREA -2Q> applying these actions to the common uses -> switch to another branch -> git checkout mybranch (a commit is specified) -> moves HEAD to point to mybranch, which means that it indirectly points to the latest commit in mybranch -> copies the data from the commit, from the REPO (object database), to the INDEX and WORKING DIRECTORY, overwriting all files (because none was specified in particular). -> restore a file to its INDEX state -> git checkout myfile.txt -> copies the data from INDEX, to the WORKING DIRECTORY, overwriting ONLY THE SPECIFIED file. -> restore a file to its commited state -> git checkout mybranch myfile.txt -> copies the data from the commit, from the REPO (object database), to the INDEX and WORKING DIRECTORY, overwriting ONLY THE SPECIFIED file. -> used -> on commit -> effectively moves the HEAD to the specified commit -> the working directory is moved into a "detached HEAD state" -> it happens when a single commit is checked out -> it means that we are no longer on a branch -> any modifications (commits) to the project does not impact any of the branches -> solution -> discard changes made in this state -> simply checkout to a branch -> the commits made in this state will be garbage collected after a while -> keep the changes made -> create a branch for the detached HEAD state -> maybe merge the branch to master -> on file -> will update the file, or files to the version in the INDEX -> here 'file' shuold be understood as 'path'. It will restore the INDEX version of a file, a directory or the whole working directory. -> on branch -> all changes must be staged or commited before the checkout -> switches to specified branch -> the working directory will be updated to reflect the branch -> the new commits will be recorded on the current branch -> on both branch/commit and path -> updates the file to the commit version. -> OPTIONS -> -b [branch] -> creates the branch and switches to it										   -> all unstaged/uncommited changes existing will be moved to the new branch -> this is used for "quickfixes" -> quick modifications on a branch that extend so much that more work is needed, and at the same time, the branch has to stay free -> the already made changes can be checked out to a branch -> the previous branch will be restored to the last commit -> if the arguments [remote]/[branch] are passed, then the newly created branch is set to track the target remote branch. Equivalent of git branch [localBranch] [remote]/[branch] -> -f [branch] -> force the checkout even though there are uncommited changes in which case discards the changes. -> --track [remote]/[branch] -> creates the local equivalent of the remote branch and switches to it												 -> sets the newly created branch to track the remote branch -> GIT BRANCH -> without any argument supplied, lists local-only branches -> [branch] -> creates a new branch -> [branch] [sha] -> creates a new branch starting from the specified commit -> [localBranch] [remote]/[branch] -> creates localBranch -> retrieves the remote branch's history into the localBranch -> sets localBranch to track the upstream remote branch -> it is the correct way to retrieve a remote branch -> OPTIONS -> -m [oldbranch] [newbranch] -> renames oldbranch to newbranch -> if oldbranch is not supplied, then it renames the current branch to newbranch -> -a / -all -> lists both remote and local branches, and the position of HEAD -> -r -> displays the remote branches -> -d [branchname] -> deletes the target branch -> if there are unmerget commits, Git will raise an error and abort the deletion -> -D [branchname] -> forces the deletion of a branch -> [localBranch] --set-upstream-to [remote]/[branch] -> sets the local existing branch to track the upstream branch from the remote repo -> achieves the same result as GIT BRANCH [localBranch] [remote]/[branch] with a few differences -> (below facts apply to git branch [localBranch] --set-upstream-to [remote]/[branch]) -> the localBranch has to exist. If it doesn't, raises an error. -> in order to work well, the remote branch has to be ahead or, at least equal, to remote master: reason: -> cloning pulls from remote master -> when created, the local branch is equal to local master, which is equal to remote master -> if remote master is ahead of remote branch, then local branch will be ahead of the remote branch it tracks -> GIT SWITCH [branch] -> switches to the branch -> OPTIONS -> -c -> creates the branch and switches to it		 -> GIT TAG [tag] -> creates a tag for the current commit -> without any options, shows a list of existing tags -> git tags will always point from the last commit, forward -> OPTIONS -> -a -> creates an annotated tag -v -> verifies a tag -s -> creates a signed tag -m [message] -> adds a message to the tag -> GIT MERGE [branch] -> merges the supplied branch into the current one -> Use case: switch to master branch then use the command on a branch. That will bring the content from the supplied branch into master. -> merging a branch into another won't delete any of them -> merging creates a new commit which has both merged commits as parents and moves HEAD (and implicitly the branch pointer) to the new commit -> when merging two files a conflict may appear which must be solved manually -> the file containing conflicting changes will contain the changes from both branches -> the changes are contained within the file markers <<<<<<< >>>>>>> and separated by ============ -> if a branch has been merged with another -> one branch moves ahead having all the content from both -> the other remains as it is										  -> if these two branches are merged again -> the first one already has all the content from both from the earlier merge -> creating a second merged commit identical to the one already existing would be wasteful -> the second branch pointer is simply moved to the merged commit -> this is called a "Fast-Forward" -> [remote]/[remoteBranch] -> merges the supplied remoteBranch of the remote, into the current branch -> OPTIONS -> --abort -> aborts the merging process and returns the working directory in its pre-merge state. -> GIT MERGETOOL -> opens the merge tool in case of merging branches and conflicts. -> GIT REBASE [branch] -> rebases the current branch on top of the branch supplied as argument (target). -> the target branch is unaffected -> the latest commit in the target branch becomes the BASE commit of the current (rebased) branch -> the latest commit from the target branch is pulled and placed between the former base and the first commit after base, effectively becoming the new base -> conflicts may appear and they must be solved -> the rebased commits are identical copies of the commits from the rebased branch -> GIT cannot "move" commits -> everything is identical except commit parents -> the rebased branch pointer will be moved to the rebased branch (copied commits) -> The original commits from the rebased branch will no longer have a branch pointer and will be garbage collected -> BASE -> is the shared commit between the two branches. Effectively, is the first commit of a branch (or where the project is branching). -> base commit won't be rebased as the state it describes has already existed in the history of the project. -> REBASING vs MERGING -> both commands have the same general effect: they merge two branches -> MERGE -> keeps the project's history intact even though confusing -> it merges both branches' histories yet shows the commits as they were made. -> REBASE -> rewrites the project's history -> it appears that the changes in the rebased branch were made after the changes in the target branch, although they were made simultaneously (different timelines) -> use cases -> clean up history before sharing a branch -> pull changes from a branch into my branch without performing a merge -> commit SQUASH -> its purpose is to combine all the commits of the source (current) branch into one -> done by using -i interactive rebase mode -> squashing is accomplsihed by -> rebasing the current branch onto the merge-base commit (the common ancestor commit of current branch with master) -> rebasing onto the merge-base commit won't create conflicts (as merge-base commit already is base of branch) and -i will allow editing the rebasing process -> during rebase, one commit, usually the oldest will be "picked" (will remain) and all the others will be "squashed" (merge into the previous until all will be merged into the picked one) -> the final commit message will be a combination of all the other commit messages but they can be edited/removed. -> OPTIONS -> -i / --interactive -> allows for an interactive rebasing process -> GIT CHERRY-PICK [commitSHA] -> applies the changes introduced in the target commit to the HEAD commit. -> it finds the changes done from the commit previous to target commit, to target commit, and replicates the same changes to the HEAD commit. -> it is different from merge because -> merge adds all the differences from both commits into one commit that contains everything. -> cherry-pick -> adds only the differences which occured between target and previous-to-target commits, to the head commit, while leaving unaffected any other files -> just replicates those changes to the HEAD commit, without merging the commits -> use cases -> a bugfix which applies to multiple versions, each version having its own branch -> used when a merge is impossible -> GIT RESET ['commit'] -> "moves commits from history into working directory/staging area or deletes them" -2Q> actually, performs two actions -> first: moves the branch ref that HEAD is pointing to, to the specified commit, basically changing the current commit in the REPOSITORY. -> second: depends on the options -> OPTIONS -> --soft -> "moves the commits back into the staging area"							                  | This first arrow is how most sources describe --soft, while the 2Q arrow describes, what it actually happens. While the overall result -2Q> second action: only moves the branch ref to the specified commit. Doesn't afffect the INDEX or the WORKING AREA. | it is basically the same, the difference is in how it happens. The commits are not 'moved' into the INDEX, it just seems like it. -> --mixed -> default option if none specified										                  | Same story here, only that after the current commit is changed, the INDEX is updated. -> "moves the commits back into the working directory"								                  | An analogy to how --soft is described above can be applied here. -2Q> second action: copies the changes from the commit you've just moved to, only to the INDEX, leaving the WORKING AREA unaffected. |							     -> common usecase -> git reset HEAD -> unstages the staged changes -2Q> the branch ref stays where it is because no other commit has been specified (can be seen as moving it to the same place it already is), and updates the INDEX with data from the REPOSITORY, overwriting any modification. -> --hard -> "deletes the changes from all the commits newer than the specified one"									| As a note on Git reset (not only--hard), it is important to know how git reset actually works, because as most sources describe it, -> "effectively makes the specified commit the latest, and moves HEAD to it"							       | it is implied that git reset is limited to a branch's history. While it is true that the most common usage of -2Q> second action: copies the changes from the commit you've just moved to, to both INDEX and WORKING AREA. | this command is to modify a branch's history, like reverting some commits, git reset has no such limitations. -2Q> effects -> hard-resetting to an older commit will result in the subsequent commits becoming unreachable and will be garbage collected.| It can be used from any branch, on any commit, even belonging to other branches, and the effects can be confusing and destructive -> completly alters the state of the project											| For instance, Git reset can be successfully used to overwrite entire branches with commits from another branches, or similar destructive operations. -> common usecases -> revert the whole project to an earlier state (previous commit) -> git reset --hard HEAD -> discard all uncommited changes from working directory and index. -> can cause data loss, so use with care -> GIT REMOTE -> with no arguments or options, lists the remotes for the current repository -> OPTIONS -> -v -> lists additional information about the remotes (such as the URLs) -> ADD [name][uri] -> adds a new remote from the [uri] to the project, locally named [name] -> can be used to clone a remote repository, however, it should be proceeded carefully: (you better use git clone. Less of a headache) reason: -> a branch with no history (on a newly initiated repo) -> is seen by git as unexisting since there are no commits the branch ref can point to															      -> cannot be set to track a remote branch, because it basically doesn't exist, so in order to track a remote branch, it has to have at least 1 commit -> by default, Git doesn't allow merging a local branch with the remote branch it is tracking, if they have different histories (the 1 commit from above). -> for the above reasons, creating a repo from scratch (git init) and adding a remote to it won't allow you to actually get the remote repo (unless using --allow-unrelated-histories) -> this case applies when trying to use "--set-upstream-to", like -> there are different ways to clone a remote repository without using git clone though: -> git checkout -b [branch] --track [remote]/[branch] -> -b instructs git to create the branch then set the upstream branch -> git branch [localBranch] [remote]/[branch] -> creates the branch and sets it to track the remote branch -> git switch [branch] -> right after git fetch -> conditions -> there must be a link to a remote repository -> the remote has to be fetched locally -> try to git switch to one of its branches -> git will automatically create a local branch with the same name -> set the newly created local branch to track its remote counterpart -> pull the remote branch to it																												     -> switch you to it -> NOTE THAT the above methods apply whenever you need to create a local branch that tracks a remote branch. Not necessarily if you have a new repo. -> another (and perhaps the intended) usage of this command, is to add a remote link to another fork of the same repository. This would allow one to concurently work with different forks of the same project -> UPDATE -> updates the remote ref branches for all remote repositories -> effectively fetches the changes -> SHOW [remote] -> shows info about the target remote -> GIT PUSH [remote] [branch] -> with no arguments, pushes the changes of the local current branch to the upstream branch of the remote repository. If the branch doesn't exist, it creates it. -> pushes the changes upstream, towards the remote repository -> git push is aborted when there are merge conflicts between local and remote -> [remote] is the upstream remote repository, [branch] is the remote branch we push to, from the current local branch -> [remote] [localbranch]:[remotebranch] -> creates the new remotebranch for the remote (a new remote branch, on the online repository, with no local equivalent) -> pushes the changes from localbranch to remotebranch -> no local branch will be set to track the remote branch -> [remote] :[remotebranch] -> deletes the remote branch -> OPTIONS -> -u / --set-upstream [remote][branch]-> sets the upstream branch -f -> force a push -> the remote repo will be updated regardless of the conflicts that may appear -tags -> pushes tags. Tags aren't pushed by default -> GIT PULL -> is a combination between GIT FETCH and GIT MERGE commands -> automatically fetches and merges the changes from the remote branch to the local branch which tracks it			   -> OPTIONS -> --rebase -> used when the upstream branch gets rebased and git pull would result in conflicts -> uses reflogs to search the common ancestor of the upstream and local branches (even thouugh it had been squashed) -> resequences the commits in the local branch by pulling the remote commits and rebasing the local commits on top of them -> GIT FETCH -> fetches the refs (branches, HEAD) and all the objects necessary to rebuild the history (the current state of the remote), from a remote (by default origin) -> effectively downloads the changes to local -> in case of a conflict, the remote branch will be separate from the local branch -> [remote] -> fetches the changes from the target remote -> [remote][branch] -> fetches the changes from the target branch of the specified remote -> OPTIONS -> --all -> fetches from all remotes -> GIT RM [file] -> the file is no longer tracked by git and is deleted -> OPTIONS -> --cached -> the file is no longer tracked by git but it is NOT deleted -> GIT MV [file] [new name] -> renames the file -> PLUMBING COMMANDS -> git hash-object [object] -> calculates the SHA1 value of an object -> OPTIONS -> --stdin -> the supplied value is taken from STDIN -> git cat-file [sha] -> displays details about a git object -> OPTIONS -> -t -> displays the type of the object whose hash is supplied -> -p -> pretty prints the object -> git count-objects -> shows the number of objects in the current project -> git show-ref [reference] -> displays all the refs containing the target word in their name -> git merge-base [branch][branch] -> shows the common ancestor commit of the two branches -> git ls-remote -> shows the remote references of the repository -> shows the remote references even without $git remote update -> CONFIGURATION -> git --version -> displays the git version -> git config [--conftype] --list -> displays the configurations -> the configuration "types" are hierarhical -> the more specific ones override the more general ones -> Repository Configuration > Global Configuration > System Configuraion -> for example it is possible to set a global user "Jim", but a specific repository to have a user "John" -> GIT CONFIG [--conftype][--action][attribute[value]] -> specifying a config type -> git config --system -> indicates a SYSTEM config attribute -> it applies to all the projects -> it usually handles more system-oriented config attributes (like the default text editor or the behaviour of "pull" command) rather than repository-oriented config attribute, like --global and --local configs handle (like the username or email address) -> git config --global -> indicates a GLOBAL config attribute -> it applies to all the projects -> Example: git config --global user.name "Name Surname" -> git config --local -> indicates a REPOSITORY config attribute -> it applies only to the current repository -> it is the default config type if a config type is not specified -> Example: -> git config --local user.name "Name Surname" -> same as: git config user.name "Name Surname" -> setting a configuration attribute -> git config [--conftype] attribute "Value " -> Example: git config --local user.name "Name Surname" -> sets the username for the current repo -> retrieving a configuration attribute -> git config [--conftype] attribute -> NO value for the attribute must be specified -> if a value is specified, then the value will be SET for the attribute -> Example: git config --local user.name -> retrieves the username of the current repository -> removing a configuration -> git config --unset [--conftype] attribute -> config files -> using git config command writes the attibutes in files -> location -> windows -> c:\users\User\.gitconfig -> global config file -> c:\program files\git\etc\.gitconfig -> system config file -> basic configuration attributes -> user.name "Name Surname" -> user.email "email@domain.com" -> core.editor "path_to_editor_exe" -> sets the default text editor -> help.autocorrect [0|1] -> autocorrects the commands inputted in bash after 0.1 second. -> set to zero to disables autocorrect -> color.ui auto -> uses colors to display info in CLI -> core.autocrlf true|false|input -> crlf - carriage return line feeds -> true: converts crlf (typically used in windows) into line feeds and stores them into a repository, and converts them back out -> false: stores crlf into a repository as they are, without converting them -> input: converts crlf into line feeds when storing them but doesn't convert them on the way out of the repo -> http.sslVerify [true|false] -> by default, Git verifies the SSL certificate of the site where a repository is cloned from -> if the site doesn't have a SSL certificate, it is expired or is self-signed, Git doesn't allow cloning the repository -> setting the http.sslVerify attribute to "false" will instruct Git to skip SSL certificate verification -> this is a big security risk

-> ALIASES -> an alias is a shortcut for a command. -> aliases are created with "git config" -> git config [--conftype] alias.[newalias] "command --options" -> "git newalias" will now be the equivalent of "git command" -> Example: git config --global alias.goad "log --graph --oneline --all --decorate" -> the aliases are stored in the config files.

-> git also has a layer of optimization which -> decides to store multiple compressed objects in the same file -> stores only the differences between files if the files are big enough and have only few differences

-> REMOTE -> is a copy of the Git repository, located somewhere else, usually the cloud -> the purpose of a remote is to -> make public a repository -> allow multiple people work on the public repository -> provide a common synchronization point for all people involved -> the actual remote tracking -> Git looks at the local branch ref and checks what commit hash it is pointing at							  -> Git looks at the remote branch ref that the local branch is tracking and checks what commit hash it is pointing at							   -> now it can calculate how many commits ahead or behind the local repo is compared to the remote (effectively the difference in commits) -> local refs and remote refs are both stored locally. The difference is that local refs are tracking the local changes and remote refs are tracking the remote changes -> a remote branch ref -> tracks the same branch (sequence of commits) as the local branch ref, but reflects the state of the branch (latest commit) from the remote repository -> REMOTE/HEAD ref determines which branch will be checked out when the repo is cloned -> REMOTE FLOW -> a git repository will obtain a remote link -> when cloning the remote repository which will automatically add a link to "origin", which is the cloned remote repository -> by manually adding a remote link using $git remote add [name][uri] -> used if remotes to different forks of the same remote are desired <> -> once a remote link has been created -> git fetch [remote] <> -> usually, when cloning, the main branch will be retrieved to local -> git branch [newlocalBranch] [remote]/[branch] -> to locally replicate a remote branch and track it											    -> <> -> git pull | -> the repos are synchronized either by pushing or pulling (fetch + merge) -> git push | -> Terms: -> FORK -> a remote clone of a remote repository. -> used to work with when the original remote repo requires permissions for regular operations -> not a concept of Git, but of the public GIT hosting services -> PULL REQUEST -> term used when there is a remote repo we have no permissions to write to				 -> if we want to modify it, we have to ASK the owner of the remote repo to pull changes from our cloned and modified repo -> PORCELAIN -> common commands used more frequently -> PLUMBING -> uncommon commands used rarely, or in scripts of some kind -> FILE STATES -> untracked -> untracked by Git -> it doesn't belong to the git repository -> tracked -> COMMITED -> files saved in a snapshot (git commit) -> MODIFIED -> files which have been modified from their last commited version -> STAGED -> modified files marked to be added in the next snapshot with git commit

-> BEST PRACTICES -> before pushing changes to the remotes -> always fetch -> merge and solve conflicts -> then push -> before merging a branch with the main branch, first fetch the changes from the remote main to the local main -> never rebase shared commits -> a common .gitignore file to prevent unwanted ignores -> README.md file in the root directory should keep all important info about the project -> frequent samller commits vs one giant commit -> coordination with the teams before large refactors -> do not rebase on a public branch -> check team guidelines about rebase -> while GIT tracks changes to any kind of file, it was not designed for/its use is not recommended for binary files.