perlgit


DESCRIPTION
       This document provides details on using git to develop Perl. If you are
       just interested in working on a quick patch, see perlhack first.  This
       document is intended for people who are regular contributors to Perl,
       including those with write access to the git repository.

CLONING THE REPOSITORY
       All of Perl's source code is kept centrally in a Git repository at
       perl5.git.perl.org.

       You can make a read-only clone of the repository by running:

         % git clone git://perl5.git.perl.org/perl.git perl

       This uses the git protocol (port 9418).

       If you cannot use the git protocol for firewall reasons, you can also
       clone via http, though this is much slower:

         % git clone http://perl5.git.perl.org/perl.git perl

WORKING WITH THE REPOSITORY
       Once you have changed into the repository directory, you can inspect
       it. After a clone the repository will contain a single local branch,
       which will be the current branch as well, as indicated by the asterisk.

         % git branch
         * blead

       Using the -a switch to "branch" will also show the remote tracking
       branches in the repository:

         % git branch -a
         * blead
           origin/HEAD
           origin/blead
         ...

       The branches that begin with "origin" correspond to the "git remote"
       that you cloned from (which is named "origin"). Each branch on the
       remote will be exactly tracked by theses branches. You should NEVER do
       work on these remote tracking branches. You only ever do work in a
       local branch. Local branches can be configured to automerge (on pull)
       from a designated remote tracking branch. This is the case with the
       default branch "blead" which will be configured to merge from the
       remote tracking branch "origin/blead".

       You can see recent commits:

         % git log

       And pull new changes from the repository, and update your local
       repository (must be clean first)
         % git fetch

       And if you want to update your remote-tracking branches for all defined
       remotes simultaneously you can do

         % git remote update

       Neither of these last two commands will update your working directory,
       however both will update the remote-tracking branches in your
       repository.

       To make a local branch of a remote branch:

         % git checkout -b maint-5.10 origin/maint-5.10

       To switch back to blead:

         % git checkout blead

   Finding out your status
       The most common git command you will use will probably be

         % git status

       This command will produce as output a description of the current state
       of the repository, including modified files and unignored untracked
       files, and in addition it will show things like what files have been
       staged for the next commit, and usually some useful information about
       how to change things. For instance the following:

         $ git status
         # On branch blead
         # Your branch is ahead of 'origin/blead' by 1 commit.
         #
         # Changes to be committed:
         #   (use "git reset HEAD <file>..." to unstage)
         #
         #       modified:   pod/perlgit.pod
         #
         # Changed but not updated:
         #   (use "git add <file>..." to update what will be committed)
         #
         #       modified:   pod/perlgit.pod
         #
         # Untracked files:
         #   (use "git add <file>..." to include in what will be committed)
         #
         #       deliberate.untracked

       This shows that there were changes to this document staged for commit,
       and that there were further changes in the working directory not yet
       staged. It also shows that there was an untracked file in the working
       directory, and as you can see shows how to change all of this. It also
       shows that there is one commit on the working branch "blead" which has
         % git pull

       It's preferable to patch against the latest blead version, since this
       is where new development occurs for all changes other than critical bug
       fixes. Critical bug fix patches should be made against the relevant
       maint branches, or should be submitted with a note indicating all the
       branches where the fix should be applied.

       Now that we have everything up to date, we need to create a temporary
       new branch for these changes and switch into it:

         % git checkout -b orange

       which is the short form of

         % git branch orange
         % git checkout orange

       Creating a topic branch makes it easier for the maintainers to rebase
       or merge back into the master blead for a more linear history. If you
       don't work on a topic branch the maintainer has to manually cherry pick
       your changes onto blead before they can be applied.

       That'll get you scolded on perl5-porters, so don't do that. Be Awesome.

       Then make your changes. For example, if Leon Brocard changes his name
       to Orange Brocard, we should change his name in the AUTHORS file:

         % perl -pi -e 's{Leon Brocard}{Orange Brocard}' AUTHORS

       You can see what files are changed:

         % git status
         # On branch orange
         # Changes to be committed:
         #   (use "git reset HEAD <file>..." to unstage)
         #
         #    modified:   AUTHORS
         #

       And you can see the changes:

         % git diff
         diff --git a/AUTHORS b/AUTHORS
         index 293dd70..722c93e 100644
         --- a/AUTHORS
         +++ b/AUTHORS
         @@ -541,7 +541,7 @@    Lars Hecking                   <lhecking@nmrc.ucc.ie>
          Laszlo Molnar                  <laszlo.molnar@eth.ericsson.se>
          Leif Huhn                      <leif@hale.dkstat.com>
          Len Johnson                    <lenjay@ibm.net>
         -Leon Brocard                   <acme@astray.com>
         +Orange Brocard                 <acme@astray.com>
          Les Peters                     <lpeters@aol.net>

       "git add FILE ..." before doing the commit. "git add --interactive"
       allows you to even just commit portions of files instead of all the
       changes in them.

       The "-m" option is used to specify the commit message. If you omit it,
       git will open a text editor for you to compose the message
       interactively. This is useful when the changes are more complex than
       the sample given here, and, depending on the editor, to know that the
       first line of the commit message doesn't exceed the 50 character legal
       maximum.

       Once you've finished writing your commit message and exited your
       editor, git will write your change to disk and tell you something like
       this:

         Created commit daf8e63: explain git status and stuff about remotes
          1 files changed, 83 insertions(+), 3 deletions(-)

       If you re-run "git status", you should see something like this:

         % git status
         # On branch blead
         # Your branch is ahead of 'origin/blead' by 2 commits.
         #
         # Untracked files:
         #   (use "git add <file>..." to include in what will be committed)
         #
         #       deliberate.untracked
         nothing added to commit but untracked files present (use "git add" to track)

       When in doubt, before you do anything else, check your status and read
       it carefully, many questions are answered directly by the git status
       output.

       You can examine your last commit with:

         % git show HEAD

       and if you are not happy with either the description or the patch
       itself you can fix it up by editing the files once more and then issue:

         % git commit -a --amend

       Now you should create a patch file for all your local changes:

         % git format-patch -M origin..
         0001-Rename-Leon-Brocard-to-Orange-Brocard.patch

       You should now send an email to to perlbug@perl.org
       <mailto:perlbug@perl.org> with a description of your changes, and
       include this patch file as an attachment. In addition to being tracked
       by RT, mail to perlbug will automatically be forwarded to perl5-porters
       (with manual moderation, so please be patient). You should only send
       patches to perl5-porters@perl.org <mailto:perl5-porters@perl.org>
         % git branch -D orange
         Deleted branch orange.

   Committing your changes
       Assuming that you'd like to commit all the changes you've made as a
       single atomic unit, run this command:

          % git commit -a

       (That "-a" tells git to add every file you've changed to this commit.
       New files aren't automatically added to your commit when you use
       "commit -a" If you want to add files or to commit some, but not all of
       your changes, have a look at the documentation for "git add".)

       Git will start up your favorite text editor, so that you can craft a
       commit message for your change. See "Commit message" in perlhack for
       more information about what makes a good commit message.

       Once you've finished writing your commit message and exited your
       editor, git will write your change to disk and tell you something like
       this:

         Created commit daf8e63: explain git status and stuff about remotes
          1 files changed, 83 insertions(+), 3 deletions(-)

       If you re-run "git status", you should see something like this:

         % git status
         # On branch blead
         # Your branch is ahead of 'origin/blead' by 2 commits.
         #
         # Untracked files:
         #   (use "git add <file>..." to include in what will be committed)
         #
         #       deliberate.untracked
         nothing added to commit but untracked files present (use "git add" to track)

       When in doubt, before you do anything else, check your status and read
       it carefully, many questions are answered directly by the git status
       output.

   Using git to send patch emails
       Please read perlhack first in order to figure out where your patches
       should be sent.

       In your ~/git/perl repository, set the destination email to perl's bug
       tracker:

         $ git config sendemail.to perlbug@perl.org

       Or maybe perl5-porters:

         $ git config sendemail.to perl5-porters@perl.org

       With this configuration, you will be prompted for your gmail password
       when you run 'git send-email'. You can also configure
       "sendemail.smtppass" with your password if you don't care about having
       your password in the .gitconfig file.

   A note on derived files
       Be aware that many files in the distribution are derivative--avoid
       patching them, because git won't see the changes to them, and the build
       process will overwrite them. Patch the originals instead. Most
       utilities (like perldoc) are in this category, i.e. patch
       utils/perldoc.PL rather than utils/perldoc. Similarly, don't create
       patches for files under $src_root/ext from their copies found in
       $install_root/lib. If you are unsure about the proper location of a
       file that may have gotten copied while building the source
       distribution, consult the "MANIFEST".

   Cleaning a working directory
       The command "git clean" can with varying arguments be used as a
       replacement for "make clean".

       To reset your working directory to a pristine condition you can do:

         % git clean -dxf

       However, be aware this will delete ALL untracked content. You can use

         % git clean -Xf

       to remove all ignored untracked files, such as build and test
       byproduct, but leave any  manually created files alone.

       If you only want to cancel some uncommitted edits, you can use "git
       checkout" and give it a list of files to be reverted, or "git checkout
       -f" to revert them all.

       If you want to cancel one or several commits, you can use "git reset".

   Bisecting
       "git" provides a built-in way to determine, with a binary search in the
       history, which commit should be blamed for introducing a given bug.

       Suppose that we have a script ~/testcase.pl that exits with 0 when some
       behaviour is correct, and with 1 when it's faulty. You need an helper
       script that automates building "perl" and running the testcase:

         % cat ~/run
         #!/bin/sh
         git clean -dxf

         # If you get './makedepend: 1: Syntax error: Unterminated quoted
         # string' when bisecting versions of perl older than 5.9.5 this hack
         # will work around the bug in makedepend.SH which was fixed in
         # version 96a8704c. Make sure to comment out `git checkout makedepend.SH'
         # below too.
         ./perl -Ilib ~/testcase.pl
         ret=$?
         [ $ret -gt 127 ] && ret=127
         # git checkout makedepend.SH
         git clean -dxf
         exit $ret

       This script may return 125 to indicate that the corresponding commit
       should be skipped. Otherwise, it returns the status of ~/testcase.pl.

       You first enter in bisect mode with:

         % git bisect start

       For example, if the bug is present on "HEAD" but wasn't in 5.10.0,
       "git" will learn about this when you enter:

         % git bisect bad
         % git bisect good perl-5.10.0
         Bisecting: 853 revisions left to test after this

       This results in checking out the median commit between "HEAD" and
       "perl-5.10.0". You can then run the bisecting process with:

         % git bisect run ~/run

       When the first bad commit is isolated, "git bisect" will tell you so:

         ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5 is first bad commit
         commit ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5
         Author: Dave Mitchell <davem@fdisolutions.com>
         Date:   Sat Feb 9 14:56:23 2008 +0000

             [perl #49472] Attributes + Unknown Error
             ...

         bisect run success

       You can peek into the bisecting process with "git bisect log" and "git
       bisect visualize". "git bisect reset" will get you out of bisect mode.

       Please note that the first "good" state must be an ancestor of the
       first "bad" state. If you want to search for the commit that solved
       some bug, you have to negate your test case (i.e. exit with 1 if OK and
       0 if not) and still mark the lower bound as "good" and the upper as
       "bad". The "first bad commit" has then to be understood as the "first
       commit where the bug is solved".

       "git help bisect" has much more information on how you can tweak your
       binary searches.  =head1 Topic branches and rewriting history

       Individual committers should create topic branches under
       yourname/some_descriptive_name. Other committers should check with a
       topic branch's creator before making any change to it.
         $ git checkout -b $branch
         $ git push origin -u $branch

       If you are not the creator of yourname/some_descriptive_name, you might
       sometimes find that the original author has edited the branch's
       history. There are lots of good reasons for this. Sometimes, an author
       might simply be rebasing the branch onto a newer source point.
       Sometimes, an author might have found an error in an early commit which
       they wanted to fix before merging the branch to blead.

       Currently the master repository is configured to forbid non-fast-
       forward merges. This means that the branches within can not be rebased
       and pushed as a single step.

       The only way you will ever be allowed to rebase or modify the history
       of a pushed branch is to delete it and push it as a new branch under
       the same name. Please think carefully about doing this. It may be
       better to sequentially rename your branches so that it is easier for
       others working with you to cherry-pick their local changes onto the new
       version. (XXX: needs explanation).

       If you want to rebase a personal topic branch, you will have to delete
       your existing topic branch and push as a new version of it. You can do
       this via the following formula (see the explanation about "refspec"'s
       in the git push documentation for details) after you have rebased your
       branch:

          # first rebase
          $ git checkout $user/$topic
          $ git fetch
          $ git rebase origin/blead

          # then "delete-and-push"
          $ git push origin :$user/$topic
          $ git push origin $user/$topic

       NOTE: it is forbidden at the repository level to delete any of the
       "primary" branches. That is any branch matching
       "m!^(blead|maint|perl)!". Any attempt to do so will result in git
       producing an error like this:

           $ git push origin :blead
           *** It is forbidden to delete blead/maint branches in this repository
           error: hooks/update exited with error code 1
           error: hook declined to update refs/heads/blead
           To ssh://perl5.git.perl.org/perl
            ! [remote rejected] blead (hook declined)
            error: failed to push some refs to 'ssh://perl5.git.perl.org/perl'

       As a matter of policy we do not edit the history of the blead and
       maint-* branches. If a typo (or worse) sneaks into a commit to blead or
       maint-*, we'll fix it in another commit. The only types of updates
       allowed on these branches are "fast-forward's", where all history is
       preserved.
       this mis-merge locally by adding the following line to your
       ".git/info/grafts" file:

         296f12bbbbaa06de9be9d09d3dcf8f4528898a49 434946e0cb7a32589ed92d18008aaa1d88515930

       It is particularly important to have this graft line if any bisecting
       is done in the area of the "merge" in question.

   Topic branches and rewriting history
       Individual committers should create topic branches under
       yourname/some_descriptive_name. Other committers should check with a
       topic branch's creator before making any change to it.

       The simplest way to create a remote topic branch that works on all
       versions of git is to push the current head as a new branch on the
       remote, then check it out locally:

         $ branch="$yourname/$some_descriptive_name"
         $ git push origin HEAD:$branch
         $ git checkout -b $branch origin/$branch

       Users of git 1.7 or newer can do it in a more obvious manner:

         $ branch="$yourname/$some_descriptive_name"
         $ git checkout -b $branch
         $ git push origin -u $branch

       If you are not the creator of yourname/some_descriptive_name, you might
       sometimes find that the original author has edited the branch's
       history. There are lots of good reasons for this. Sometimes, an author
       might simply be rebasing the branch onto a newer source point.
       Sometimes, an author might have found an error in an early commit which
       they wanted to fix before merging the branch to blead.

       Currently the master repository is configured to forbid non-fast-
       forward merges. This means that the branches within can not be rebased
       and pushed as a single step.

       The only way you will ever be allowed to rebase or modify the history
       of a pushed branch is to delete it and push it as a new branch under
       the same name. Please think carefully about doing this. It may be
       better to sequentially rename your branches so that it is easier for
       others working with you to cherry-pick their local changes onto the new
       version. (XXX: needs explanation).

       If you want to rebase a personal topic branch, you will have to delete
       your existing topic branch and push as a new version of it. You can do
       this via the following formula (see the explanation about "refspec"'s
       in the git push documentation for details) after you have rebased your
       branch:

          # first rebase
          $ git checkout $user/$topic
          $ git fetch
           *** It is forbidden to delete blead/maint branches in this repository
           error: hooks/update exited with error code 1
           error: hook declined to update refs/heads/blead
           To ssh://perl5.git.perl.org/perl
            ! [remote rejected] blead (hook declined)
            error: failed to push some refs to 'ssh://perl5.git.perl.org/perl'

       As a matter of policy we do not edit the history of the blead and
       maint-* branches. If a typo (or worse) sneaks into a commit to blead or
       maint-*, we'll fix it in another commit. The only types of updates
       allowed on these branches are "fast-forward's", where all history is
       preserved.

       Annotated tags in the canonical perl.git repository will never be
       deleted or modified. Think long and hard about whether you want to push
       a local tag to perl.git before doing so. (Pushing unannotated tags is
       not allowed.)

WRITE ACCESS TO THE GIT REPOSITORY
       Once you have write access, you will need to modify the URL for the
       origin remote to enable pushing. Edit .git/config with the
       git-config(1) command:

         % git config remote.origin.url ssh://perl5.git.perl.org/perl.git

       You can also set up your user name and e-mail address. Most people do
       this once globally in their ~/.gitconfig by doing something like:

         % git config --global user.name "var Arnfjoer` Bjarmason"
         % git config --global user.email avarab@gmail.com

       However if you'd like to override that just for perl then execute then
       execute something like the following in perl:

         % git config user.email avar@cpan.org

       It is also possible to keep "origin" as a git remote, and add a new
       remote for ssh access:

         % git remote add camel perl5.git.perl.org:/perl.git

       This allows you to update your local repository by pulling from
       "origin", which is faster and doesn't require you to authenticate, and
       to push your changes back with the "camel" remote:

         % git fetch camel
         % git push camel

       The "fetch" command just updates the "camel" refs, as the objects
       themselves should have been fetched when pulling from "origin".  =head1
       Accepting a patch

       If you have received a patch file generated using the above section,
       you should try out the patch.
       If just a raw diff is provided, it is also possible use this two-step
       process:

         % git apply bugfix.diff
         % git commit -a -m "Some fixing" --author="That Guy <that.guy@internets.com>"

       Now we can inspect the change:

         % git show HEAD
         commit b1b3dab48344cff6de4087efca3dbd63548ab5e2
         Author: Leon Brocard <acme@astray.com>
         Date:   Fri Dec 19 17:02:59 2008 +0000

           Rename Leon Brocard to Orange Brocard

         diff --git a/AUTHORS b/AUTHORS
         index 293dd70..722c93e 100644
         --- a/AUTHORS
         +++ b/AUTHORS
         @@ -541,7 +541,7 @@ Lars Hecking                        <lhecking@nmrc.ucc.ie>
          Laszlo Molnar                  <laszlo.molnar@eth.ericsson.se>
          Leif Huhn                      <leif@hale.dkstat.com>
          Len Johnson                    <lenjay@ibm.net>
         -Leon Brocard                   <acme@astray.com>
         +Orange Brocard                 <acme@astray.com>
          Les Peters                     <lpeters@aol.net>
          Lesley Binks                   <lesley.binks@gmail.com>
          Lincoln D. Stein               <lstein@cshl.org>

       If you are a committer to Perl and you think the patch is good, you can
       then merge it into blead then push it out to the main repository:

         % git checkout blead
         % git merge experimental
         % git push

       If you want to delete your temporary branch, you may do so with:

         % git checkout blead
         % git branch -d experimental
         error: The branch 'experimental' is not an ancestor of your current HEAD.
         If you are sure you want to delete it, run 'git branch -D experimental'.
         % git branch -D experimental
         Deleted branch experimental.

   Committing to blead
       The 'blead' branch will become the next production release of Perl.

       Before pushing any local change to blead, it's incredibly important
       that you do a few things, lest other committers come after you with
       pitchforks and torches:

       o   Make sure you have a good commit message. See "Commit message" in
           perlhack for details.
           This will run basic sanity checks. To see which sanity checks, have
           a look in t/porting.

       o   If you make any changes that affect miniperl or core routines that
           have different code paths for miniperl, be sure to run "make
           minitest".  This will catch problems that even the full test suite
           will not catch because it runs a subset of tests under miniperl
           rather than perl.

   Committing to maintenance versions
       Maintenance versions should only be altered to add critical bug fixes,
       see perlpolicy.

       To commit to a maintenance version of perl, you need to create a local
       tracking branch:

         % git checkout --track -b maint-5.005 origin/maint-5.005

       This creates a local branch named "maint-5.005", which tracks the
       remote branch "origin/maint-5.005". Then you can pull, commit, merge
       and push as before.

       You can also cherry-pick commits from blead and another branch, by
       using the "git cherry-pick" command. It is recommended to use the -x
       option to "git cherry-pick" in order to record the SHA1 of the original
       commit in the new commit message.

       Before pushing any change to a maint version, make sure you've
       satisfied the steps in "Committing to blead" above.

   Grafts
       The perl history contains one mistake which was not caught in the
       conversion: a merge was recorded in the history between blead and
       maint-5.10 where no merge actually occurred. Due to the nature of git,
       this is now impossible to fix in the public repository. You can remove
       this mis-merge locally by adding the following line to your
       ".git/info/grafts" file:

         296f12bbbbaa06de9be9d09d3dcf8f4528898a49 434946e0cb7a32589ed92d18008aaa1d88515930

       It is particularly important to have this graft line if any bisecting
       is done in the area of the "merge" in question.

   Merging from a branch via GitHub
       While we don't encourage the submission of patches via GitHub, that
       will still happen. Here is a guide to merging patches from a GitHub
       repository.

         % git remote add avar git://github.com/avar/perl.git
         % git fetch avar

       Now you can see the differences between the branch and blead:

         % git diff avar/orange

       And then push back to the repository:

         % git push

   A note on camel and dromedary
       The committers have SSH access to the two servers that serve
       "perl5.git.perl.org". One is "perl5.git.perl.org" itself (camel), which
       is the 'master' repository. The second one is
       "users.perl5.git.perl.org" (dromedary), which can be used for general
       testing and development. Dromedary syncs the git tree from camel every
       few minutes, you should not push there. Both machines also have a full
       CPAN mirror in /srv/CPAN, please use this. To share files with the
       general public, dromedary serves your ~/public_html/ as
       "http://users.perl5.git.perl.org/~yourlogin/"

       These hosts have fairly strict firewalls to the outside. Outgoing, only
       rsync, ssh and git are allowed. For http and ftp, you can use
       http://webproxy:3128 as proxy. Incoming, the firewall tries to detect
       attacks and blocks IP addresses with suspicious activity. This
       sometimes (but very rarely) has false positives and you might get
       blocked. The quickest way to get unblocked is to notify the admins.

       These two boxes are owned, hosted, and operated by booking.com. You can
       reach the sysadmins in #p5p on irc.perl.org or via mail to
       "perl5-porters@perl.org".



perl v5.14.2                      2011-09-26                        PERLGIT(1)
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