X-Git-Url: https://git.phdru.name/?a=blobdiff_plain;f=pep-git.txt;h=a9b4d9ea3b37911fbdc6431541bc7a419946637c;hb=3464b8a43624f0a795e7a0b2908304cd4a661a70;hp=d995d2456fe367ceaa1d0fa0a8081274497d2e2c;hpb=021099ec5db6e77e41c480d68c3c0312d7cabffa;p=git-wiki.git diff --git a/pep-git.txt b/pep-git.txt index d995d24..a9b4d9e 100644 --- a/pep-git.txt +++ b/pep-git.txt @@ -14,7 +14,7 @@ Abstract This Informational PEP collects information about git. There is, of course, a lot of documentation for git, so the PEP concentrates on -more complex issues, topics and scenarios. +more complex issues, scenarios and topics. The plan is to extend the PEP in the future collecting information about equivalence of Mercurial and git scenarios to help migrating @@ -75,18 +75,27 @@ Download and installation Unix users: download and install using your package manager. Microsoft Windows: download `git-for-windows -`_. +`_ or `msysGit +`_. MacOS X: use git installed with `XCode -`_ or download +`_ or download from +`MacPorts `_ or `git-osx-installer -`_. +`_ 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. Initial configuration --------------------- This simple code is often appears in documentation, but it is -important so let repeat it here:: +important so let repeat it here. Git stores author and committer +names/emails in every commit, so configure your real name and +preferred email:: $ git config --global user.name "User Name" $ git config --global user.email user.name@example.org @@ -98,26 +107,245 @@ 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``. Usually the currently -checked out branch is ``v2``. +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:: + + $ git clone -b v2 http://git.python.org/python.git + $ cd python + $ git branch v1 origin/v1 + +The last command creates a new local branch v1 and sets +remotes/origin/v1 as its upstream remote branch. + +The same result can achieved with commands:: + + $ git clone -b v1 http://git.python.org/python.git + $ cd python + $ git checkout --track origin/v2 + +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. + + +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. +Labels, on the other hand, can be created, moved, renamed and deleted +freely. + + +Remote repository 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 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:: + + $ git branch -rv + +To see local and remote 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. + +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. + +Updating local and remote branches +---------------------------------- + +There is a major difference between + +:: + + $ git fetch REMOTE BRANCH + +and + +:: + + $ 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 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 first command is used internally by ``git pull``. + +:: + + $ git pull REMOTE BRANCH + +is equivalent to + +:: + + $ git fetch REMOTE BRANCH + $ git merge FETCH_HEAD # FETCH_HEAD is a literal here + +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 merge v1 + +If you have not yet pushed commits on ``v1``, though, the scenario has +to become a bit more complex. Git refuses to update +non-fast-forwardable branch, and you don't want to do force-pull +because that would remove your non-pushed commits and you would need +to recover. So you want to rebase ``v1`` but you cannot rebase +non-current branch. Hence, checkout ``v1`` and rebase it before +merging:: + + $ git checkout v1 + $ git pull --rebase origin v1 + $ git checkout v2 + $ git pull --rebase origin v2 + $ git merge v1 + +It is possible to configure git to make it fetch/pull a few branches +or all branches at once, so you can simply run + +:: + + $ git pull origin + +or even + +:: + + $ git pull + +Push +'''' + +Pushing is a bit simpler. There is only one command ``push``. When you +run + +:: + + $ git push origin v1 v2 + +git guesses (knowing upstream remote branches) that you really want + +:: + + $ git push origin v1:v1 v2:v2 + +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, +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 +editing and caveats`_ below. + +It is possible to configure git to make it push a few branches or all +branches at once, so you can simply run + +:: + + $ git push origin + +or even + +:: + + $ git push + +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 +repositories git prefers pull-based workflow. + +When you want to deploy code on a remote host and can only use push +(because your workstation is behind a firewall and you cannot pull +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. + +Tags +'''' + +Git automatically fetches tags that point to commits being fetched +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... + +For example:: + + $ git fetch origin tag 1.4.2 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:: + + $ git push origin tag 1.4.2 + $ git push origin v1 v2 tag 2.1.7 + +Don't move tags with ``git tag -f`` after they have been published. Commit editing and caveats ========================== A warning not to edit published (pushed) commits also appears in -documentation but it's also repeated here as it's very important. +documentation but it's repeated here anyway as it's very important. 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 see the head of the -remote branch:: +To see what commits have not been published yet compare the head of the +branch with its upstream remote branch:: $ git log origin/v2.. + $ git log origin/v1..v1 For every branch that has an upstream remote branch git maintains an -alias @{upstream} (short version @{u}):: +alias @{upstream} (short version @{u}), so the commands above can be +given as:: $ git log @{u}.. $ git log v1@{u}..v1 @@ -126,14 +354,154 @@ To see the status of all branches:: $ git branch -avv +To compare the status of local branches with a remote repo:: + + $ git remote show origin + 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 commits that hasn'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 already been pushed. +safely edit, remove, reorder, combine and split commits that hasn'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 +already been pushed. Not a problem until commits are in a public +or shared repository. + + +Undo +==== + +TODO: describe undo strategies: git reset, git revert, git checkout, +git reflog. "Commit early, commit often". + +How to undo a merge +https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html + + +Merge or rebase? +================ + +Internet is full of heated discussions on the topic: "merge or +rebase?" Most of them are meaningless. When a DVCS is being used in a +big team with a big and complex project with many branches there is +simply no way to avoid merges. So the question diminished to "whether +to use rebase, and if yes - when to use rebase?" Considering that it +is very much recommended not to rebase published commits the question +diminished even further: "whether to use rebase on non-pushed +commits?" + +That small question is for the team to decide. The author of the PEP +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 + +and configure rebase for existing branches:: + + $ git config branch.NAME.rebase true + +After that ``git pull origin v2`` will be equivalent to ``git pull +--rebase origin v2``. + +In case when merge is preferred it is recommended to create new +commits in a separate feature or topic branch while using rebase to +update the mainline branch. When the topic branch is ready merge it +into mainline. To avoid a tedious task of resolving conflicts you can +merge the topic branch to the mainline from time to time and switch +back to the topic branch to continue working on it. The entire +workflow would be something like:: + + $ git checkout -b issue-42 # create and switch to a new branch + ...edit/test/commit... + $ git checkout v2 + $ git pull --rebase origin v2 # update v2 from the upstream + $ git merge issue-42 + $ git branch -d issue-42 # delete the topic branch + $ git push origin v2 + +When the topic branch is deleted only the label is removed, commits +are stayed in the database, they are now merged into v2:: + + --o--o--o--o--o--o-M-`_ and +`IndexCommandQuickref +`_ in Git +Wiki. + + +Advanced configuration +====================== + +Line endings +------------ + +Git has builtin mechanisms to handle line endings. + +TODO: describe crlf configuration and .gitattributes. + + +Database maintenance +==================== + +TODO: dangling objects, git gc, git repack. + + +Tips and tricks +=============== + +TODO: sticky options; example: git grep -O. + +TODO: bash/zsh completion, bash/zsh prompt. + + +git on server +============= + +TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab. + + +From Mercurial to git +===================== + +Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts + +https://github.com/felipec/git-remote-hg + +https://hg-git.github.io/ References