X-Git-Url: https://git.phdru.name/?p=git-wiki.git;a=blobdiff_plain;f=pep-git.txt;h=aa86ef8f8fa0bd59e0394eb8286e7e33a8f8b2de;hp=4cbedf62b90518b76f02adb2565cde2c7395e5df;hb=af24d7c3f871f5f8e21e1a7ba2750f212f201489;hpb=ab8f276ae1a7c24ba145764144be8f87870282ac diff --git a/pep-git.txt b/pep-git.txt index 4cbedf6..aa86ef8 100644 --- a/pep-git.txt +++ b/pep-git.txt @@ -62,7 +62,7 @@ many different languages. Download Russian translation from `GArik Offline documentation --------------------- -Git has builtin help: run ``git help TOPIC``. For example, run +Git has builtin help: run ``git help $TOPIC``. For example, run ``git help git`` or ``git help help``. @@ -72,7 +72,8 @@ Quick start Download and installation ------------------------- -Unix users: download and install using your package manager. +Unix users: `download and install using your package manager +`_. Microsoft Windows: download `git-for-windows `_ or `msysGit @@ -85,9 +86,8 @@ MacOS X: use git installed with `XCode `_ or install git with `Homebrew `_: ``brew install git``. -`git-cola `_ is a sleek and -powerful Git GUI written in Python and GPL licensed. Linux, Windows, -MacOS X. +`git-cola `_ is a Git GUI +written in Python and GPL licensed. Linux, Windows, MacOS X. `TortoiseGit `_ is a Windows Shell Interface to Git based on TortoiseSVN; open source. @@ -110,31 +110,31 @@ Examples in this PEP Examples of git commands in this PEP use the following approach. It is supposed that you, the user, works with a local repository named ``python`` that has an upstream remote repo named ``origin``. Your -local repo has two branches ``v1`` and ``v2``. For most examples the -currently checked out branch is ``v2``. That is, it's assumed you have -done something like that:: +local repo has two branches ``v1`` and ``master``. For most examples +the currently checked out branch is ``master``. That is, it's assumed +you have done something like that:: - $ git clone -b v2 http://git.python.org/python.git + $ git clone http://git.python.org/python.git $ cd python $ git branch v1 origin/v1 The first command clones remote repository into local directory -`python``, creates a new local branch v2, sets remotes/origin/v2 as -its upstream remote branch and checks it out into the working -directory. +`python``, creates a new local branch master, sets +remotes/origin/master as its upstream remote-tracking branch and +checks it out into the working directory. The last command creates a new local branch v1 and sets -remotes/origin/v1 as its upstream remote branch. +remotes/origin/v1 as its upstream remote-tracking branch. The same result can be achieved with commands:: $ git clone -b v1 http://git.python.org/python.git $ cd python - $ git checkout --track origin/v2 + $ git checkout --track origin/master -The last command creates a new local branch v2, sets -remotes/origin/v2 as its upstream remote branch and checks it out into -the working directory. +The last command creates a new local branch master, sets +remotes/origin/master as its upstream remote-tracking branch and +checks it out into the working directory. Branches and branches @@ -143,96 +143,93 @@ Branches and branches Git terminology can be a bit misleading. Take, for example, the term "branch". In git it has two meanings. A branch is a directed line of commits (possibly with merges). And a branch is a label or a pointer -assigned to a line of commits. It is important to differentiate when -you talk about commits and when about their labels. Lines of commits -are by itself unnamed and are usually only lengthening and merging. +assigned to a line of commits. It is important to distinguish when you +talk about commits and when about their labels. Lines of commits are +by itself unnamed and are usually only lengthening and merging. Labels, on the other hand, can be created, moved, renamed and deleted freely. -Remote repository and remote branches -===================================== +Remote repositories and remote branches +======================================= -Another example of slightly misleading terminology. Remote -repositories are really remote, you access them via network (well, a -remote repository can be on your local disk, but it's still remote -because it's not the current repo). +Remote-tracking branches are branches (pointers to commits) in your +local repository. They are there for you to remember what branches and +commits have been pulled from and pushed to what remote repos (you can +pull from and push to many remotes). Remote-tracking branches live +under ``remotes/$REMOTE`` namespaces, e.g. ``remotes/origin/master``. -Remote branches, on the other hand, are branches (pointers to commits) -in your local repository. They are there for you to remember what -branches and commits have been pulled from and pushed to what remote -repos (you can pull from and push to many remotes). Remote branches -live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``. - -To see the status of remote branches run:: +To see the status of remote-tracking branches run:: $ git branch -rv -To see local and remote branches (and tags) pointing to commits:: +To see local and remote-tracking branches (and tags) pointing to +commits:: $ git log --decorate -You never do your own development on remote branches. You create a -local branch that has a remote branch as upstream and do development -on that local branch. On push git updates remote branches, and on pull -git updates remote branches and fast-forwards, merges or rebases local -branches. +You never do your own development on remote-tracking branches. You +create a local branch that has a remote branch as upstream and do +development on that local branch. On push git pushes commits to the +remote repo and updates remote-tracking branches, on pull git fetches +commits from the remote repo, updates remote-tracking branches and +fast-forwards, merges or rebases local branches. When you do an initial clone like this:: $ git clone -b v1 http://git.python.org/python.git git clones remote repository ``http://git.python.org/python.git`` to -directory ``python``, creates remote branches, creates a local branch -``v1``, configure it to track upstream remotes/origin/v1 branch and -checks out ``v1`` into the working directory. +directory ``python``, creates remote-tracking branches, creates a +local branch ``v1``, configure it to track upstream remotes/origin/v1 +branch and checks out ``v1`` into the working directory. -Updating local and remote branches ----------------------------------- +Updating local and remote-tracking branches +------------------------------------------- There is a major difference between :: - $ git fetch REMOTE BRANCH + $ git fetch $REMOTE $BRANCH and :: - $ git fetch REMOTE BRANCH:BRANCH + $ git fetch $REMOTE $BRANCH:$BRANCH -The first command fetches commits from the named BRANCH in the REMOTE -repository that are not in your repository and leaves the id (the -hash) of the head commit in file .git/FETCH_HEAD. But it doesn't -update any branch (doesn't move any pointer). +The first command fetches commits from the named $BRANCH in the +$REMOTE repository that are not in your repository, updates +remote-tracking branch and leaves the id (the hash) of the head commit +in file .git/FETCH_HEAD. -The second command fetches commits from the named BRANCH in the REMOTE -repository that are not in your repository and updates both the local -branch BRANCH and its upstream remote branch. But it refuses to update -branches in case of non-fast-forward. And it refuses to update the -current branch. +The second command fetches commits from the named $BRANCH in the +$REMOTE repository that are not in your repository and updates both +the local branch $BRANCH and its upstream remote-tracking branch. But +it refuses to update branches in case of non-fast-forward. And it +refuses to update the current branch. The first command is used internally by ``git pull``. :: - $ git pull REMOTE BRANCH + $ git pull $REMOTE $BRANCH is equivalent to :: - $ git fetch REMOTE BRANCH - $ git merge FETCH_HEAD # FETCH_HEAD is a literal here + $ git fetch $REMOTE $BRANCH + $ git merge FETCH_HEAD -Certainly, BRANCH in that case should be your current branch. If you +Certainly, $BRANCH in that case should be your current branch. If you want to merge a different branch into your current branch first update that non-current branch and then merge:: $ git fetch origin v1:v1 # Update v1 - $ git pull --rebase origin v2 # Update the current branch v2 using - # rebase instead of merge + $ git pull --rebase origin master # Update the current branch master + # using rebase instead of merge $ git merge v1 If you have not yet pushed commits on ``v1``, though, the scenario has @@ -245,8 +242,8 @@ merging:: $ git checkout v1 $ git pull --rebase origin v1 - $ git checkout v2 - $ git pull --rebase origin v2 + $ git checkout master + $ git pull --rebase origin master $ git merge v1 It is possible to configure git to make it fetch/pull a few branches @@ -262,6 +259,10 @@ or even $ git pull +Default remote repository for fetching/pulling is origin. Default set +of references to fetch is calculated using matching algorithm: git +fetches all branches having the same name on both ends. + Push '''' @@ -270,19 +271,18 @@ run :: - $ git push origin v1 v2 - -git guesses (knowing upstream remote branches) that you really want + $ git push origin v1 master -:: +git pushes local v1 to remote v1 and local master to remote master. +The same as:: - $ git push origin v1:v1 v2:v2 + $ git push origin v1:v1 master:master -Git pushes commits to the remote repo and updates remote branches. Git -refuses to push commits that aren't fast-forwardable. You can -force-push anyway, but please remember - you can force-push to your -own repositories but don't force-push to public or shared repos. If -you find git refuses to push commits that aren't fast-forwardable, +Git pushes commits to the remote repo and updates remote-tracking +branches. Git refuses to push commits that aren't fast-forwardable. +You can force-push anyway, but please remember - you can force-push to +your own repositories but don't force-push to public or shared repos. +If you find git refuses to push commits that aren't fast-forwardable, better fetch and merge commits from the remote repo (or rebase your commits on top of the fetched commits), then push. Only force-push if you know what you do and why you do it. See the section `Commit @@ -301,6 +301,21 @@ or even $ git push +Default remote repository for pushing is origin. Default set +of references to push in git before 2.0 is calculated using matching +algorithm: git pushes all branches having the same name on both ends. +Default set of references to push in git 2.0+ is calculated using +simple algorithm: git pushes the current branch back to its +@{upstream}. + +To configure git before 2.0 to the new behaviour run:: + +$ git config push.default simple + +To configure git 2.0+ to the old behaviour run:: + +$ git config push.default matching + Git refuses to push a branch if it's the current branch in the remote non-bare repository: git refuses to update remote working directory. You really should push only to bare repositories. For non-bare @@ -312,6 +327,11 @@ from it) you do that in two steps using two repositories: you push from the workstation to a bare repo on the remote host, ssh to the remote host and pull from the bare repo to a non-bare deployment repo. +That changed in git 2.3, but see `the blog post +`_ +for caveats; in 2.4 the push-to-deploy feature was `further improved +`_. + Tags '''' @@ -320,20 +340,34 @@ during fetch/pull. To fetch all tags (and commits they point to) run ``git fetch --tags origin``. To fetch some specific tags fetch them explicitly:: - $ git fetch origin tag TAG1 tag TAG2... + $ git fetch origin tag $TAG1 tag $TAG2... For example:: - $ git fetch origin tag 1.4.2 tag 2.1.7 + $ git fetch origin tag 1.4.2 + $ git fetch origin v1:v1 tag 2.1.7 Git doesn't automatically pushes tags. That allows you to have private -tags (lightweight tags are also private for a repo, they cannot be -pushed). To push tags list them explicitly:: +tags. To push tags list them explicitly:: $ git push origin tag 1.4.2 - $ git push origin v1 v2 tag 2.1.7 + $ git push origin v1 master tag 2.1.7 + +Don't move tags with ``git tag -f`` or remove tags with ``git tag -d`` +after they have been published. + +Private information +''''''''''''''''''' -Don't move tags with ``git tag -f`` after they have been published. +When cloning/fetching/pulling/pushing git copies only database objects +(commits, trees, files and tags) and symbolic references (branches and +lightweight tags). Everything else is private to the repository and +never cloned, updated or pushed. It's your config, your hooks, your +private exclude file. + +If you want to distribute hooks, copy them to the working tree, add, +commit, push and instruct the team to update ind install the hook +manually. Commit editing and caveats @@ -346,14 +380,14 @@ It is possible to recover from forced push but it's PITA for the entire team. Please avoid it. To see what commits have not been published yet compare the head of the -branch with its upstream remote branch:: +branch with its upstream remote-tracking branch:: - $ git log origin/v2.. + $ git log origin/master.. $ git log origin/v1..v1 -For every branch that has an upstream remote branch git maintains an -alias @{upstream} (short version @{u}), so the commands above can be -given as:: +For every branch that has an upstream remote-tracking branch git +maintains an alias @{upstream} (short version @{u}), so the commands +above can be given as:: $ git log @{u}.. $ git log v1@{u}..v1 @@ -371,9 +405,9 @@ Read `how to recover from upstream rebase It is in ``git help rebase``. On the other hand don't be too afraid about commit editing. You can -safely edit, remove, reorder, combine and split commits that hasn't +safely edit, remove, reorder, combine and split commits that haven't been pushed yet. You can even push commits to your own (backup) repo, -edit them later and force-push edited commits to replace what has +edit them later and force-push edited commits to replace what have already been pushed. Not a problem until commits are in a public or shared repository. @@ -382,23 +416,125 @@ Undo ==== Whatever you do, don't panic. Almost anything in git can be undone. + +git checkout: restore file's content +------------------------------------ + ``git checkout``, for example, can be used to restore the content of file(s) to that one of a commit. Like this:: git checkout HEAD~ README -The commands restores the contente of README file to the last but one -commit in the current branch. By default a commit ID is simple HEAD; +The commands restores the contents of README file to the last but one +commit in the current branch. By default the commit ID is simply HEAD; i.e. ``git checkout README`` restores README to the latest commit. (Do not use ``git checkout`` to view a content of a file in a commit, use ``git cat-file -p``; e.g. ``git cat-file -p HEAD~:path/to/README``). -TODO: describe undo strategies: git reset, git revert, -git reflog. "Commit early, commit often". +git reset: remove (non-pushed) commits +-------------------------------------- -How to undo a merge -https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html +``git reset`` moves the head of the current branch. The head can be +moved to point to any commit but it's often used to remove a commit or +a few (preferably, non-pushed ones) from the top of the branch - that +is, to move the branch backward in order to undo a few (non-pushed) +commits. + +``git reset`` has three modes of operation - soft, hard and mixed. +Default is mixed. ProGit `explains +`_ the +difference very clearly. Bare repositories don't have indices or +working trees so in a bare repo only soft reset is possible. + +Unstaging +''''''''' + +Mixed mode reset with a path or paths can be used to unstage changes - +that is, to remove from index changes added with ``git add`` for +committing. See `The Book +`_ for details +about unstaging and other undo tricks. + +git reflog: reference log +------------------------- + +Removing commits with ``git reset`` or moving the head of a branch +sounds dangerous and it is. But there is a way to undo: another +reset back to the original commit. Git doesn't remove commits +immediately; unreferenced commits (in git terminology they are called +"dangling commits") stay in the database for some time (default is two +weeks) so you can reset back to it or create a new branch pointing to +the original commit. + +For every move of a branch's head - with ``git commit``, ``git +checkout``, ``git fetch``, ``git pull``, ``git rebase``, ``git reset`` +and so on - git stores a reference log (reflog for short). For every +move git stores where the head was. Command ``git reflog`` can be used +to view (and manipulate) the log. + +In addition to the moves of the head of every branch git stores the +moves of the HEAD - a symbolic reference that (usually) names the +current branch. HEAD is changed with ``git checkout $BRANCH``. + +By default ``git reflog`` shows the moves of the HEAD, i.e. the +command is equivalent to ``git reflog HEAD``. To show the moves of the +head of a branch use the command ``git reflog $BRANCH``. + +So to undo a ``git reset`` lookup the original commit in ``git +reflog``, verify it with ``git show`` or ``git log`` and run ``git +reset $COMMIT_ID``. Git stores the move of the branch's head in +reflog, so you can undo that undo later again. + +In a more complex situation you'd want to move some commits along with +resetting the head of the branch. Cherry-pick them to the new branch. +For example, if you want to reset the branch ``master`` back to the +original commit but preserve two commits created in the current branch +do something like:: + + $ git branch save-master # create a new branch saving master + $ git reflog # find the original place of master + $ git reset $COMMIT_ID + $ git cherry-pick save-master~ save-master + $ git branch -D save-master # remove temporary branch + +git revert: revert a commit +--------------------------- + +``git revert`` reverts a commit or commits, that is, it creates a new +commit or commits that revert(s) the effects of the given commits. +It's the only way to undo published commits (``git commit --amend``, +``git rebase`` and ``git reset`` change the branch in +non-fast-forwardable ways so they should only be used for non-pushed +commits.) + +There is a problem with reverting a merge commit. ``git revert`` can +undo the code created by the merge commit but it cannot undo the fact +of merge. See the discussion `How to revert a faulty merge +`_. + +One thing that cannot be undone +------------------------------- + +Whatever you undo, there is one thing that cannot be undone - +overwritten uncommitted changes. Uncommitted changes don't belong to +git so git cannot help preserving them. + +Most of the time git warns you when you're going to execute a command +that overwrites uncommitted changes. Git warns you when you try to +switch branches with ``git checkout``. It warns you when you're going +to rebase with non-clean working tree. It refuses to pull new commits +over non-committed files. + +But there are commands that do exactly that - overwrite files in the +working tree. Commands like ``git checkout $PATHs`` or ``git reset +--hard`` silently overwrite files including your uncommitted changes. + +With that in mind you can understand the stance "commit early, commit +often". Commit as often as possible. Commit on every save in your +editor or IDE. You can edit your commits before pushing - change, +reorder, combine, remove. But save your changes in git database, +either commit changes or at least stash them with ``git stash``. Merge or rebase? @@ -418,19 +554,19 @@ recommends to use rebase when pulling, i.e. always do ``git pull --rebase`` or even configure automatic setup of rebase for every new branch:: - $ git config branch.autosetuprebase true + $ git config branch.autosetuprebase always and configure rebase for existing branches:: - $ git config branch.NAME.rebase true + $ git config branch.$NAME.rebase true For example:: $ git config branch.v1.rebase true - $ git config branch.v2.rebase true + $ git config branch.master.rebase true -After that ``git pull origin v2`` becomes equivalent to ``git pull ---rebase origin v2``. +After that ``git pull origin master`` becomes equivalent to ``git pull +--rebase origin master``. In case when merge is preferred it is recommended to create new commits in a separate feature or topic branch while using rebase to @@ -442,18 +578,18 @@ on it. The entire workflow would be something like:: $ git checkout -b issue-42 # create a new issue branch and switch to it ...edit/test/commit... - $ git checkout v2 - $ git pull --rebase origin v2 # update v2 from the upstream + $ git checkout master + $ git pull --rebase origin master # update master from the upstream $ git merge issue-42 $ git branch -d issue-42 # delete the topic branch - $ git push origin v2 + $ git push origin master When the topic branch is deleted only the label is removed, commits -are stayed in the database, they are now merged into v2:: +are stayed in the database, they are now merged into master:: - o--o--o--o--o--M--< v2 - the mainline branch + o--o--o--o--o--M--< master - the mainline branch \ / - --*--*--* - the topic branch, now unnamed + --*--*--* - the topic branch, now unnamed The topic branch is deleted to avoid cluttering branch namespace with small topic branches. Information on what issue was fixed or what @@ -463,16 +599,37 @@ feature was implemented should be in the commit messages. Null-merges =========== -Git has a builtin strategy for what Python core developers call +Git has a builtin merge strategy for what Python core developers call "null-merge":: - $ git merge -s ours v1 # null-merge v1 into v2 + $ git merge -s ours v1 # null-merge v1 into master -ReReRe -====== +Advanced configuration +====================== -https://git-scm.com/book/en/Git-Tools-Rerere +Line endings +------------ + +Git has builtin mechanisms to handle line endings between platforms +with different EOL styles. To allow git to do CRLF conversion assign +``text`` attribute to files using `.gitattributes +`_. +For files that have to have specific line ending assign ``eol`` +attribute. For binary files the attribute is, naturally, ``binary``. + +For example:: + + $ cat .gitattributes + *.py text + *.txt text + *.png binary + /readme.txt eol=CRLF + +To check what attributes git uses for files use ``git check-attr`` +command. For example:: + +$ git check-attr -a -- \*.py Advanced topics @@ -481,31 +638,53 @@ Advanced topics Staging area ------------ -Staging area aka index is a distinguishing feature of git. See -`WhatIsTheIndex +Staging area aka index aka cache is a distinguishing feature of git. +Staging area is where git collects patches before committing them. +Separation between collecting patches and commit phases provides a +very useful feature of git: one can review collected patches before +commit and even edit them - remove some hunks, add new hunks and +review again. + +To add files to the index use ``git add``. Collecting patches before +committing means you need to do that for every change, not only to add +new (untracked) files. To simplify committing in case you just want to +commit everything without reviewing run ``git commit --all`` (or just +``-a``) - the command adds every changed tracked file to the index and +then commit. + +To add hunks of patches to the index use ``git add --patch`` (or just +``-p``). To remove collected files from the index use ``git reset HEAD +-- $FILE...`` To add/inspect/remove collected hunks use ``git add +--interactive`` (``-i``). + +To see the diff between the index and the last commit (i.e., collected +patches) use ``git diff --cached``. To see the diff between the +working tree and the index (i.e., uncollected patches) use just ``git +diff``. To see the diff between the working tree and the last commit +(i.e., both collected and uncollected patches) use ``git diff HEAD``. + +See `WhatIsTheIndex `_ and `IndexCommandQuickref `_ in Git Wiki. -Advanced configuration -====================== - -Line endings ------------- - -Git has builtin mechanisms to handle line endings. +ReReRe +====== -TODO: describe crlf configuration and .gitattributes. +https://git-scm.com/book/en/Git-Tools-Rerere Database maintenance ==================== TODO: dangling objects, git gc, git repack. + https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html +http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html + Tips and tricks ===============