X-Git-Url: https://git.phdru.name/?a=blobdiff_plain;ds=sidebyside;f=pep-git.txt;h=c2bb7dd07271fe886f2a8978076fd05de7d2c887;hb=93ea7a95b31831f5b416fbcd7b7999f9d9fc78a7;hp=2a2c67633d6175aefd2f9a838ad1759314c22f06;hpb=dd1409cca5a4422a825a66b930b7382b43defb4d;p=git-wiki.git diff --git a/pep-git.txt b/pep-git.txt index 2a2c676..c2bb7dd 100644 --- a/pep-git.txt +++ b/pep-git.txt @@ -1,9 +1,9 @@ PEP: XXX -Title: git +Title: Collecting information about git Version: $Revision$ Last-Modified: $Date$ Author: Oleg Broytman -Status: Active +Status: Draft Type: Informational Content-Type: text/x-rst Created: 01-Jun-2015 @@ -12,10 +12,525 @@ Post-History: 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, 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 +Python development from Mercurial to git. + +The author of the PEP doesn't currently plan to write a Process PEP on +migration from Mercurial to git. + + +Documentation +============= + +Git is accompanied with a lot of documentation, both online and +offline. + +Documentation for starters +-------------------------- + +Git Tutorial: `part 1 +`_, +`part 2 +`_. + +`Git User's manual +`_. +`Everyday GIT With 20 Commands Or So +`_. +`Git workflows +`_. + +Advanced documentation +---------------------- + +`Git Magic +`_, +also with a number of translations. + +`Pro Git `_. The Book about git. Buy it at +Amazon or download in PDF, mobi, or ePub form. Has translations to +many different languages. Download Russian translation from `GArik +`_. + +`Git Wiki `_. + +Offline documentation +--------------------- + +Git has builtin help: run ``git help TOPIC``. For example, run +``git help git`` or ``git help help``. + + +Quick start +=========== + +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 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. + +`TortoiseGit `_ is a Windows Shell Interface +to Git based on TortoiseSVN; open source. + +Initial configuration +--------------------- + +This simple code is often appears in documentation, but it is +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 + + +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:: + + $ git clone -b v2 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. + +The last command creates a new local branch v1 and sets +remotes/origin/v1 as its upstream remote 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 + +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 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 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}), so the commands above can be +given as:: + + $ git log @{u}.. + $ git log v1@{u}..v1 + +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, 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://www.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's 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's 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 + +For example:: + + $ git config branch.v1.rebase true + $ git config branch.v2.rebase true + +After that ``git pull origin v2`` becomes 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 large number of +conflicts at once 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--M--< v2 - the mainline branch + \ / + --*--*--* - 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 +feature was implemented should be in the commit messages. + + +Null-merges +=========== + +Git has a builtin strategy for what Python core developers call +"null-merge":: + + $ git merge -s ours v1 # null-merge v1 into v2 + + +ReReRe +====== + +https://git-scm.com/book/en/Git-Tools-Rerere + + +Advanced topics +=============== + +Staging area +------------ + +Staging area aka index is a distinguishing feature of git. See +`WhatIsTheIndex +`_ 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. +https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html + + +Tips and tricks +=============== + +TODO: sticky options; example: git grep -O. + +TODO: tricky options; example: git log -p3. + +TODO: bash/zsh completion, bash/zsh prompt. +https://git.kernel.org/cgit/git/git.git/tree/contrib/completion + + +git on server +============= + +TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab. + +http://gitolite.com/gitolite/index.html + +https://git.kernel.org/cgit/git/git.git/tree/gitweb + +http://git.zx2c4.com/cgit/ + +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 ========== +.. [] + Copyright =========