[Python-checkins] peps: PEP 13
barry.warsaw
python-checkins at python.org
Tue Sep 15 00:12:45 CEST 2015
https://hg.python.org/peps/rev/07406baeafac
changeset: 6058:07406baeafac
user: Barry Warsaw <barry at python.org>
date: Mon Sep 14 18:12:42 2015 -0400
summary:
PEP 13
files:
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+PEP: 13
+Title: Collecting information about git
+Version: $Revision$
+Last-Modified: $Date$
+Author: Oleg Broytman <phd at phdru.name>
+Status: Draft
+Type: Informational
+Content-Type: text/x-rst
+Created: 01-Jun-2015
+Post-History: 12-Sep-2015
+
+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 (and more related to Python development) issues,
+scenarios and examples.
+
+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 Python development from Mercurial to git.
+
+
+Documentation
+=============
+
+Git is accompanied with a lot of documentation, both online and
+offline.
+
+
+Documentation for starters
+--------------------------
+
+Git Tutorial: `part 1
+<https://www.kernel.org/pub/software/scm/git/docs/gittutorial.html>`_,
+`part 2
+<https://www.kernel.org/pub/software/scm/git/docs/gittutorial-2.html>`_.
+
+`Git User's manual
+<https://www.kernel.org/pub/software/scm/git/docs/user-manual.html>`_.
+`Everyday GIT With 20 Commands Or So
+<https://www.kernel.org/pub/software/scm/git/docs/giteveryday.html>`_.
+`Git workflows
+<https://www.kernel.org/pub/software/scm/git/docs/gitworkflows.html>`_.
+
+
+Advanced documentation
+----------------------
+
+`Git Magic
+<http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html>`_,
+with a number of translations.
+
+`Pro Git <https://git-scm.com/book>`_. The Book about git. Buy it at
+Amazon or download in PDF, mobi, or ePub form. It has translations to
+many different languages. Download Russian translation from `GArik
+<https://github.com/GArik/progit/wiki>`_.
+
+`Git Wiki <https://git.wiki.kernel.org/index.php/Main_Page>`_.
+
+
+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
+<https://git-scm.com/download/linux>`_.
+
+Microsoft Windows: download `git-for-windows
+<https://github.com/git-for-windows/git/releases>`_ or `msysGit
+<https://github.com/msysgit/msysgit/releases>`_.
+
+MacOS X: use git installed with `XCode
+<https://developer.apple.com/xcode/downloads/>`_ or download from
+`MacPorts <https://www.macports.org/ports.php?by=name&substr=git>`_ or
+`git-osx-installer
+<http://sourceforge.net/projects/git-osx-installer/files/>`_ or
+install git with `Homebrew <http://brew.sh/>`_: ``brew install git``.
+
+`git-cola <https://git-cola.github.io/index.html>`_ is a Git GUI
+written in Python and GPL licensed. Linux, Windows, MacOS X.
+
+`TortoiseGit <https://tortoisegit.org/>`_ 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 at 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 ``master``. For most examples
+the currently checked out branch is ``master``. That is, it's assumed
+you have done something like that::
+
+ $ git clone https://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 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-tracking branch.
+
+The same result can be achieved with commands::
+
+ $ git clone -b v1 https://git.python.org/python.git
+ $ cd python
+ $ git checkout --track origin/master
+
+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
+=====================
+
+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 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 repositories and remote branches
+=======================================
+
+Remote-tracking branches are branches (pointers to commits) in your
+local repository. They are there for git (and 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``.
+
+To see the status of remote-tracking branches run::
+
+ $ git branch -rv
+
+To see local and remote-tracking branches (and tags) pointing to
+commits::
+
+ $ git log --decorate
+
+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 https://git.python.org/python.git
+
+git clones remote repository ``https://git.python.org/python.git`` to
+directory ``python``, creates a remote named ``origin``, 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-tracking 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, 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-tracking branch. But
+it refuses to update branches in case of non-fast-forward. And it
+refuses to update the current branch (currently checked out branch,
+where HEAD is pointing to).
+
+The first command is used internally by ``git pull``.
+
+::
+
+ $ git pull $REMOTE $BRANCH
+
+is equivalent to
+
+::
+
+ $ git fetch $REMOTE $BRANCH
+ $ git merge FETCH_HEAD
+
+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 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
+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 master
+ $ git pull --rebase origin master
+ $ 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
+
+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
+''''
+
+Pushing is a bit simpler. There is only one command ``push``. When you
+run
+
+::
+
+ $ 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 master:master
+
+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
+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
+
+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 doesn't allow 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.
+
+That changed in git 2.3, but see `the blog post
+<https://github.com/blog/1957-git-2-3-has-been-released#push-to-deploy>`_
+for caveats; in 2.4 the push-to-deploy feature was `further improved
+<https://github.com/blog/1994-git-2-4-atomic-pushes-push-to-deploy-and-more#push-to-deploy-improvements>`_.
+
+
+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
+ $ git fetch origin v1:v1 tag 2.1.7
+
+Git doesn't automatically pushes tags. That allows you to have private
+tags. To push tags list them explicitly::
+
+ $ git push origin tag 1.4.2
+ $ git push origin v1 master tag 2.1.7
+
+Or push all tags at once::
+
+ $ git push --tags origin
+
+Don't move tags with ``git tag -f`` or remove tags with ``git tag -d``
+after they have been published.
+
+
+Private information
+'''''''''''''''''''
+
+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 and install the hooks
+manually.
+
+
+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 a 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-tracking branch::
+
+ $ git log origin/master.. # from origin/master to HEAD (of master)
+ $ git log origin/v1..v1 # from origin/v1 to the head of v1
+
+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
+
+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
+<https://git-scm.com/docs/git-rebase#_recovering_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, reorder, remove, 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 have
+already been pushed. Not a problem until commits are in a public
+or shared repository.
+
+
+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 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``).
+
+
+git reset: remove (non-pushed) commits
+--------------------------------------
+
+``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
+<https://git-scm.com/book/en/Git-Tools-Reset-Demystified>`_ 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
+<https://git-scm.com/book/en/Git-Basics-Undoing-Things>`_ 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
+<https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html>`_.
+
+
+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 doesn't allow you to switch
+branches with ``git checkout``. It stops 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 - edit commit
+messages, change commits, reorder, combine, split, remove. But save
+your changes in git database, either commit changes or at least stash
+them with ``git stash``.
+
+
+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 always
+
+and configure rebase for existing branches::
+
+ $ git config branch.$NAME.rebase true
+
+For example::
+
+ $ git config branch.v1.rebase true
+ $ git config branch.master.rebase true
+
+After that ``git pull origin master`` becomes equivalent to ``git pull
+--rebase origin master``.
+
+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 a new issue branch and switch to it
+ ...edit/test/commit...
+ $ 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 master
+
+When the topic branch is deleted only the label is removed, commits
+are stayed in the database, they are now merged into master::
+
+ o--o--o--o--o--M--< master - 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 merge strategy for what Python core developers call
+"null-merge"::
+
+ $ git merge -s ours v1 # null-merge v1 into master
+
+
+Advanced configuration
+======================
+
+Line endings
+------------
+
+Git has builtin mechanisms to handle line endings between platforms
+with different end-of-line styles. To allow git to do CRLF conversion
+assign ``text`` attribute to files using `.gitattributes
+<https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html>`_.
+For files that have to have specific line endings 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
+===============
+
+Staging area
+------------
+
+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: you 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 commit a file or files regardless of patches collected
+in the index run ``git commit [--only|-o] -- $FILE...``.
+
+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) run ``git diff HEAD``.
+
+See `WhatIsTheIndex
+<https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
+`IndexCommandQuickref
+<https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
+Wiki.
+
+
+ReReRe
+======
+
+Rerere is a mechanism that helps to resolve repeated merge conflicts.
+The most frequent source of recurring merge conflicts are topic
+branches that are merged into mainline and then the merge commits are
+removed; that's often performed to test the topic branches and train
+rerere; merge commits are removed to have clean linear history and
+finish the topic branch with only one last merge commit.
+
+Rerere works by remembering the states of tree before and after a
+successful commit. That way rerere can automatically resolve conflicts
+if they appear in the same files.
+
+Rerere can be used manually with ``git rerere`` command but most often
+it's used automatically. Enable rerere with these commands in a
+working tree::
+
+ $ git config rerere.enabled true
+ $ git config rerere.autoupdate true
+
+You don't need to turn rerere on globally - you don't want rerere in
+bare repositories or single-branche repositories; you only need rerere
+in repos where you often perform merges and resolve merge conflicts.
+
+See `Rerere <https://git-scm.com/book/en/Git-Tools-Rerere>`_ in The
+Book.
+
+
+Database maintenance
+====================
+
+Git object database and other files/directories under ``.git`` require
+periodic maintenance and cleanup. For example, commit editing left
+unreferenced objects (dangling objects, in git terminology) and these
+objects should be pruned to avoid collecting cruft in the DB. The
+command ``git gc`` is used for maintenance. Git automatically runs
+``git gc --auto`` as a part of some commands to do quick maintenance.
+Users are recommended to run ``git gc --aggressive`` from time to
+time; ``git help gc`` recommends to run it every few hundred
+changesets; for more intensive projects it should be something like
+once a week and less frequently (biweekly or monthly) for lesser
+active projects.
+
+``git gc --aggressive`` not only removes dangling objects, it also
+repacks object database into indexed and better optimized pack(s); it
+also packs symbolic references (branches and tags). Another way to do
+it is to run ``git repack``.
+
+There is a well-known `message
+<https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html>`_ from Linus
+Torvalds regarding "stupidity" of ``git gc --aggressive``. The message
+can safely be ignored now. It is old and outdated, ``git gc
+--aggressive`` became much better since that time.
+
+For those who still prefer ``git repack`` over ``git gc --aggressive``
+the recommended parameters are ``git repack -a -d -f --depth=20
+--window=250``. See `this detailed experiment
+<http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html>`_
+for explanation of the effects of these parameters.
+
+From time to time run ``git fsck [--strict]`` to verify integrity of
+the database. ``git fsck`` may produce a list of dangling objects;
+that's not an error, just a reminder to perform regular maintenance.
+
+
+Tips and tricks
+===============
+
+Command-line options and arguments
+----------------------------------
+
+`git help cli
+<https://www.kernel.org/pub/software/scm/git/docs/gitcli.html>`_
+recommends not to combine short options/flags. Most of the times
+combining works: ``git commit -av`` works perfectly, but there are
+situations when it doesn't. E.g., ``git log -p -5`` cannot be combined
+as ``git log -p5``.
+
+Some options have arguments, some even have default arguments. In that
+case the argument for such option must be spelled in a sticky way:
+``-Oarg``, never ``-O arg`` because for an option that has a default
+argument the latter means "use default value for option ``-O`` and
+pass ``arg`` further to the option parser". For example, ``git grep``
+has an option ``-O`` that passes a list of names of the found files to
+a program; default program for ``-O`` is a pager (usually ``less``),
+but you can use your editor::
+
+ $ git grep -Ovim # but not -O vim
+
+BTW, if git is instructed to use ``less`` as the pager (i.e., if pager
+is not configured in git at all it uses ``less`` by default, or if it
+gets ``less`` from GIT_PAGER or PAGER environment variables, or if it
+was configured with ``git config --global core.pager less``, or
+``less`` is used in the command ``git grep -Oless``) ``git grep``
+passes ``+/$pattern`` option to ``less`` which is quite convenient.
+Unfortunately, ``git grep`` doesn't pass the pattern if the pager is
+not exactly ``less``, even if it's ``less`` with parameters (something
+like ``git config --global core.pager less -FRSXgimq``); fortunately,
+``git grep -Oless`` always passes the pattern.
+
+
+bash/zsh completion
+-------------------
+
+It's a bit hard to type ``git rebase --interactive --preserve-merges
+HEAD~5`` manually even for those who are happy to use command-line,
+and this is where shell completion is of great help. Bash/zsh come
+with programmable completion, often automatically installed and
+enabled, so if you have bash/zsh and git installed, chances are you
+are already done - just go and use it at the command-line.
+
+If you don't have necessary bits installed, install and enable
+bash_completion package. If you want to upgrade your git completion to
+the latest and greatest download necessary file from `git contrib
+<https://git.kernel.org/cgit/git/git.git/tree/contrib/completion>`_.
+
+Git-for-windows comes with git-bash for which bash completion is
+installed and enabled.
+
+
+bash/zsh prompt
+---------------
+
+For command-line lovers shell prompt can carry a lot of useful
+information. To include git information in the prompt use
+`git-prompt.sh
+<https://git.kernel.org/cgit/git/git.git/tree/contrib/completion/git-prompt.sh>`_.
+Read the detailed instructions in the file.
+
+Search the Net for "git prompt" to find other prompt variants.
+
+
+git on server
+=============
+
+The simplest way to publish a repository or a group of repositories is
+``git daemon``. The daemon provides anonymous access, by default it is
+read-only. The repositories are accessible by git protocol (git://
+URLs). Write access can be enabled but the protocol lacks any
+authentication means, so it should be enabled only within a trusted
+LAN. See ``git help daemon`` for details.
+
+Git over ssh provides authentication and repo-level authorisation as
+repositories can be made user- or group-writeable (see parameter
+``core.sharedRepository`` in ``git help config``). If that's too
+permissive or too restrictive for some project's needs there is a
+wrapper `gitolite <http://gitolite.com/gitolite/index.html>`_ that can
+be configured to allow access with great granularity; gitolite is
+written in Perl and has a lot of documentation.
+
+Web interface to browse repositories can be created using `gitweb
+<https://git.kernel.org/cgit/git/git.git/tree/gitweb>`_ or `cgit
+<http://git.zx2c4.com/cgit/about/>`_. Both are CGI scripts (written in
+Perl and C). In addition to web interface both provide read-only dumb
+http access for git (http(s):// URLs).
+
+There are also more advanced web-based development environments that
+include ability to manage users, groups and projects; private,
+group-accessible and public repositories; they often include issue
+trackers, wiki pages, pull requests and other tools for development
+and communication. Among these environments are `Kallithea
+<https://kallithea-scm.org/>`_ and `pagure <https://pagure.io/>`_,
+both are written in Python; pagure was written by Fedora developers
+and is being used to develop some Fedora projects. `Gogs
+<http://gogs.io/>`_ is written in Go; there is a fork `Gitea
+<http://gitea.io/>`_.
+
+And last but not least, `Gitlab <https://about.gitlab.com/>`_. It's
+perhaps the most advanced web-based development environment for git.
+Written in Ruby, community edition is free and open source (MIT
+license).
+
+
+From Mercurial to git
+=====================
+
+There are many tools to convert Mercurial repositories to git. The
+most famous are, probably, `hg-git <https://hg-git.github.io/>`_ and
+`fast-export <http://repo.or.cz/w/fast-export.git>`_ (many years ago
+it was known under the name ``hg2git``).
+
+But a better tool, perhaps the best, is `git-remote-hg
+<https://github.com/felipec/git-remote-hg>`_. It provides transparent
+bidirectional (pull and push) access to Mercurial repositories from
+git. Its author wrote a `comparison of alternatives
+<https://github.com/felipec/git/wiki/Comparison-of-git-remote-hg-alternatives>`_
+that seems to be mostly objective.
+
+To use git-remote-hg, install or clone it, add to your PATH (or copy
+script ``git-remote-hg`` to a directory that's already in PATH) and
+prepend ``hg::`` to Mercurial URLs. For example::
+
+ $ git clone https://github.com/felipec/git-remote-hg.git
+ $ PATH=$PATH:"`pwd`"/git-remote-hg
+ $ git clone hg::https://hg.python.org/peps/ PEPs
+
+To work with the repository just use regular git commands including
+``git fetch/pull/push``.
+
+To start converting your Mercurial habits to git see the page
+`Mercurial for Git users
+<https://mercurial.selenic.com/wiki/GitConcepts>`_ at Mercurial wiki.
+At the second half of the page there is a table that lists
+corresponding Mercurial and git commands. Should work perfectly in
+both directions.
+
+Python Developer's Guide also has a chapter `Mercurial for git
+developers <https://docs.python.org/devguide/gitdevs.html>`_ that
+documents a few differences between git and hg.
+
+
+Copyright
+=========
+
+This document has been placed in the public domain.
+
+
+
+..
+ Local Variables:
+ mode: indented-text
+ indent-tabs-mode: nil
+ sentence-end-double-space: t
+ fill-column: 70
+ coding: utf-8
+ End:
+ vim: set fenc=us-ascii tw=70 :
--
Repository URL: https://hg.python.org/peps
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