Major revision of perlhack and perlrepository

The existing perlhack is huge and takes a long time to get to key
information like "how to submit a patch". It also contains a massive
amount of (very useful) detail on the Perl interpreter, debugging,
portability issues, and so on.

Some parts of perlhack are just obsolete. For example, Larry really
isn't deeply involved on p5p any more.

Meanwhile, perlrepository _also_ contains a lot of useful information
on patching Perl, as well as a small git tutorial focused on working
with the Perl repository.

Taken together, the two documents overlap and conflict with each other.

This commit does the following:

== Reconcile conflicts and overlaps, remove obsolete information

I've separated out distinct pieces of information and organized them
into individual pod files. More on that below. I've also removed anything
that was obviously out of date.

== Make it easier for casual contributors to contribute.

The perlhack document now gets to "how to make a patch" very quickly. My
assumption is that most contributors to Perl are doing something small,
like fixing pod, adding a test, etc.

The documentation aimed at people doing more extensive hacking is still
there, but it's been moved so that it comes at the end of the document
or has been moved to another document.

I've made an effort to cross-reference the various documents so that
nothing gets lost.

== Get to the point

The perlhack document had a lot of discussion of general Perl culture.
I've trimmed a lot of this and moved some of it so it comes later.

== Per-file summary

=== perlrepository.pod

This is gone. Some of its content is now in perlhack. This includes
the bits on writing good commit messages, how (and where) to submit a
patch, etc.

The rest is now called perlgit, and is _only_ a git how-to.

=== perlhack.pod

This has been cut down quite a bit.

I changed the opening so it starts with a quick guide to submitting
small patches.

The document covers bug reporting, the p5p list, a quick how-to on
getting the source (including git, gitweb, and rsync), and a lot of
general information on patching perl and running tests.

Much of this material was already present, but I've done a fair amount
of editing for modernization and clarity.

Most of the information specific to C-level hacking has been moved to
other documents.

=== perlsource.pod

This is a guide to the Perl source tree. Most of the content was extracted
from perlhack. I've edited existing content and added details on some
parts of the tree that weren't covered.

=== perlinterp.pod

This is a tour of the Perl interpreter source and a walkthrough of
how it works that originally lived in perlhack. This has received very
little editing.

=== perlhacktut.pod

This is a walkthrough of creating a sample patch to the C core code that
originally lived in perlhack. This has received very little editing.

=== perlhacktips.pod

The perlhack document contained a lot of useful information on low-level
hacking details like debugging, compilation issues, portability, etc.
This has received very little editing.

I did remove some bits on ancient stuff related to Tru64 and IRIX.

1 files changed, 0 insertions, 1003 deletions

diff --git a/pod/perlrepository.pod b/pod/perlrepository.pod
deleted file mode 100644
index 350b1283b5..0000000000
--- a/pod/perlrepository.pod
+++ /dev/null
@@ -1,1003 +0,0 @@
-=encoding utf8
-
-=for comment
-Consistent formatting of this file is achieved with:
-  perl ./Porting/podtidy pod/perlrepository.pod
-
-=head1 NAME
-
-perlrepository - Using the Perl source repository
-
-=head1 SYNOPSIS
-
-All of Perl's source code is kept centrally in a Git repository at
-I<perl5.git.perl.org>. The repository contains many Perl revisions from
-Perl 1 onwards and all the revisions from Perforce, the version control
-system we were using previously. This repository is accessible in
-different ways.
-
-The full repository takes up about 80MB of disk space. A check out of
-the blead branch (that is, the main development branch, which contains
-bleadperl, the development version of perl 5) takes up about 160MB of
-disk space (including the repository). A build of bleadperl takes up
-about 200MB (including the repository and the check out).
-
-=head1 Getting access to the repository
-
-=head2 Read access via the web
-
-You may access the repository over the web. This allows you to browse
-the tree, see recent commits, subscribe to RSS feeds for the changes,
-search for particular commits and more. You may access it at:
-
-  http://perl5.git.perl.org/perl.git
-
-A mirror of the repository is found at:
-
-  http://github.com/mirrors/perl
-
-=head2 Read access via Git
-
-You will need a copy of Git for your computer. You can fetch a copy of
-the repository using the Git protocol (which uses port 9418):
-
-  % git clone git://perl5.git.perl.org/perl.git perl-git
-
-This clones the repository and makes a local copy in the F<perl-git>
-directory.
-
-If your local network does not allow you to use port 9418, then you can
-fetch a copy of the repository over HTTP (this is at least 4x slower):
-
-  % git clone http://perl5.git.perl.org/perl.git perl-http
-
-This clones the repository and makes a local copy in the F<perl-http>
-directory.
-
-=head2 Write access to the repository
-
-If you are a committer, then you can fetch a copy of the repository
-that you can push back on with:
-
-  % git clone ssh://perl5.git.perl.org/perl.git perl-ssh
-
-This clones the repository and makes a local copy in the F<perl-ssh>
-directory.
-
-If you cloned using the git protocol, which is faster than ssh, then
-you will need to modify the URL for the origin remote to enable
-pushing. To do that edit F<.git/config> with git-config(1) like this:
-
-  % 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 F<~/.gitconfig> by doing something like:
-
-  % git config --global user.name "Ævar Arnfjörð 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 F<perl-git>:
-
-  % git config user.email avar@cpan.org
-
-It is also possible to keep C<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
-C<origin>, which is faster and doesn't require you to authenticate, and
-to push your changes back with the C<camel> remote:
-
-  % git fetch camel
-  % git push camel
-
-The C<fetch> command just updates the C<camel> refs, as the objects
-themselves should have been fetched when pulling from C<origin>.
-
-=head2 A note on camel and dromedary
-
-The committers have SSH access to the two servers that serve
-C<perl5.git.perl.org>. One is C<perl5.git.perl.org> itself (I<camel>),
-which is the 'master' repository. The second one is
-C<users.perl5.git.perl.org> (I<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
-C<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
-C<perl5-porters@perl.org>
-
-=head1 Overview of 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 C<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 C<blead> which will be configured to merge from the
-remote tracking branch C<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 pull
-
-Assuming we are on the branch C<blead> immediately after a pull, this
-command would be more or less equivalent to:
-
-  % git fetch
-  % git merge origin/blead
-
-In fact if you want to update your local repository without touching
-your working directory you do:
-
-  % 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
-
-=head2 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/perlrepository.pod
-  #
-  # Changed but not updated:
-  #   (use "git add <file>..." to update what will be committed)
-  #
-  #       modified:   pod/perlrepository.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 C<blead> which has
-not been pushed to the C<origin> remote yet. B<NOTE>: that this output
-is also what you see as a template if you do not provide a message to
-C<git commit>.
-
-Assuming that you'd like to commit all the changes you've just made as
-a a single atomic unit, run this command:
-
-   % git commit -a
-
-(That C<-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
-C<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 C<git add>.)
-
-Git will start up your favorite text editor, so that you can craft a
-commit message for your change. See L</Commit message> below 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 C<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.
-
-=head1 Submitting a patch
-
-If you have a patch in mind for Perl, you should first get a copy of
-the repository:
-
-  % git clone git://perl5.git.perl.org/perl.git perl-git
-
-Then change into the directory:
-
-  % cd perl-git
-
-Alternatively, if you already have a Perl repository, you should ensure
-that you're on the I<blead> branch, and your repository is up to date:
-
-  % git checkout blead
-  % 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>
-   Lesley Binks                   <lesley.binks@gmail.com>
-   Lincoln D. Stein               <lstein@cshl.org>
-
-For changes significant enough to warrant a F<pod/perldelta.pod> entry, the
-porters would greatly appreciate it if you submit an entry along with your
-actual change. Significant changes include, but are not limited to:
-
-=over 4
-
-=item *
-
-adding, deprecating, or removing core features
-
-=item *
-
-adding, deprecating, removing, or upgrading core or dual-life modules
-
-=item *
-
-adding new core tests
-
-=item *
-
-fixing security issues and user-visible bugs in the core
-
-=item *
-
-changes that might break existing code, either on the perl or C level
-
-=item *
-
-significant performance improvements
-
-=item *
-
-adding, removing, or significantly changing documentation in the F<pod/>
-directory
-
-=item *
-
-important platform-specific changes
-
-=back
-
-Please make sure you add the perldelta entry to the right section within
-F<pod/perldelta.pod>. More information on how to write good perldelta entries is
-available in the C<Style> section of F<Porting/how_to_write_a_perldelta.pod>.
-
-Now commit your change locally:
-
-  % git commit -a -m 'Rename Leon Brocard to Orange Brocard'
-  Created commit 6196c1d: Rename Leon Brocard to Orange Brocard
-   1 files changed, 1 insertions(+), 1 deletions(-)
-
-The C<-a> option is used to include all files that git tracks that you have
-changed.  If at this time, you only want to commit some of the files you have
-worked on, you can omit the C<-a> and use the command C<S<git add I<FILE ...>>>
-before doing the commit.  C<S<git add --interactive>> allows you to even just
-commit portions of files instead of all the changes in them.
-
-The C<-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.
-
-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
-L<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 L<perl5-porters@perl.org|mailto:perl5-porters@perl.org>
-directly if the patch is not ready to be applied, but intended for discussion.
-
-See the next section for how to configure and use git to send these
-emails for you.
-
-If you want to delete your temporary branch, you may do so with:
-
-  % git checkout blead
-  % git branch -d orange
-  error: The branch 'orange' is not an ancestor of your current HEAD.
-  If you are sure you want to delete it, run 'git branch -D orange'.
-  % git branch -D orange
-  Deleted branch orange.
-
-=head2 Using git to send patch emails
-
-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 (discussed above):
-
-  $ git config sendemail.to perl5-porters@perl.org
-
-Then you can use git directly to send your patch emails:
-
-  $ git send-email 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
-
-You may need to set some configuration variables for your particular
-email service provider. For example, to set your global git config to
-send email via a gmail account:
-
-  $ git config --global sendemail.smtpserver smtp.gmail.com
-  $ git config --global sendemail.smtpssl 1
-  $ git config --global sendemail.smtpuser YOURUSERNAME@gmail.com
-
-With this configuration, you will be prompted for your gmail password
-when you run 'git send-email'.  You can also configure
-C<sendemail.smtppass> with your password if you don't care about having
-your password in the .gitconfig file.
-
-=head2 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
-F<utils/perldoc.PL> rather than F<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 C<MANIFEST>.
-
-=for XXX
-What should we recommend about binary files now? Do we need anything?
-
-=head2 Getting your patch accepted
-
-If you are submitting a code patch there are several things that you
-need to do.
-
-=over 4
-
-=item Commit message
-
-As you craft each patch you intend to submit to the Perl core, it's
-important to write a good commit message.
-
-The first line of the commit message should be a short description and
-should skip the full stop. It should be no longer than the subject line
-of an E-Mail, 50 characters being a good rule of thumb.
-
-A lot of Git tools (Gitweb, GitHub, git log --pretty=oneline, ..) will
-only display the first line (cut off at 50 characters) when presenting
-commit summaries.
-
-The commit message should include description of the problem that the
-patch corrects or new functionality that the patch adds.
-
-As a general rule of thumb, your commit message should let a programmer
-with a reasonable familiarity with the Perl core quickly understand
-what you were trying to do, how you were trying to do it and why the
-change matters to Perl.
-
-=over 4
-
-=item What
-
-Your commit message should describe what part of the Perl core you're
-changing and what you expect your patch to do.
-
-=item Why
-
-Perhaps most importantly, your commit message should describe why the
-change you are making is important. When someone looks at your change
-in six months or six years, your intent should be clear.  If you're
-deprecating a feature with the intent of later simplifying another bit
-of code, say so. If you're fixing a performance problem or adding a new
-feature to support some other bit of the core, mention that.
-
-=item How
-
-While it's not necessary for documentation changes, new tests or
-trivial patches, it's often worth explaining how your change works.
-Even if it's clear to you today, it may not be clear to a porter next
-month or next year.
-
-=back
-
-A commit message isn't intended to take the place of comments in your
-code.  Commit messages should describe the change you made, while code
-comments should describe the current state of the code.  If you've just
-implemented a new feature, complete with doc, tests and well-commented
-code, a brief commit message will often suffice.  If, however, you've
-just changed a single character deep in the parser or lexer, you might
-need to write a small novel to ensure that future readers understand
-what you did and why you did it.
-
-=item Comments, Comments, Comments
-
-Be sure to adequately comment your code.  While commenting every line
-is unnecessary, anything that takes advantage of side effects of
-operators, that creates changes that will be felt outside of the
-function being patched, or that others may find confusing should be
-documented.  If you are going to err, it is better to err on the side
-of adding too many comments than too few.
-
-=item Style
-
-In general, please follow the particular style of the code you are
-patching.
-
-In particular, follow these general guidelines for patching Perl
-sources:
-
-    8-wide tabs (no exceptions!)
-    4-wide indents for code, 2-wide indents for nested CPP #defines
-    try hard not to exceed 79-columns
-    ANSI C prototypes
-    uncuddled elses and "K&R" style for indenting control constructs
-    no C++ style (//) comments
-    mark places that need to be revisited with XXX (and revisit often!)
-    opening brace lines up with "if" when conditional spans multiple
-        lines; should be at end-of-line otherwise
-    in function definitions, name starts in column 0 (return value is on
-        previous line)
-    single space after keywords that are followed by parens, no space
-        between function name and following paren
-    avoid assignments in conditionals, but if they're unavoidable, use
-        extra paren, e.g. "if (a && (b = c)) ..."
-    "return foo;" rather than "return(foo);"
-    "if (!foo) ..." rather than "if (foo == FALSE) ..." etc.
-
-=item Testsuite
-
-If your patch changes code (rather than just changing documentation)
-you should also include one or more test cases which illustrate the bug
-you're fixing or validate the new functionality you're adding.  In
-general, you should update an existing test file rather than create a
-new one.
-
-Your testsuite additions should generally follow these guidelines
-(courtesy of Gurusamy Sarathy <gsar@activestate.com>):
-
-    Know what you're testing.  Read the docs, and the source.
-    Tend to fail, not succeed.
-    Interpret results strictly.
-    Use unrelated features (this will flush out bizarre interactions).
-    Use non-standard idioms (otherwise you are not testing TIMTOWTDI).
-    Avoid using hardcoded test numbers whenever possible (the
-      EXPECTED/GOT found in t/op/tie.t is much more maintainable,
-      and gives better failure reports).
-    Give meaningful error messages when a test fails.
-    Avoid using qx// and system() unless you are testing for them.  If you
-      do use them, make sure that you cover _all_ perl platforms.
-    Unlink any temporary files you create.
-    Promote unforeseen warnings to errors with $SIG{__WARN__}.
-    Be sure to use the libraries and modules shipped with the version
-      being tested, not those that were already installed.
-    Add comments to the code explaining what you are testing for.
-    Make updating the '1..42' string unnecessary.  Or make sure that
-      you update it.
-    Test _all_ behaviors of a given operator, library, or function:
-      - All optional arguments
-      - Return values in various contexts (boolean, scalar, list, lvalue)
-      - Use both global and lexical variables
-      - Don't forget the exceptional, pathological cases.
-
-=back
-
-=head1 Accepting a patch
-
-If you have received a patch file generated using the above section,
-you should try out the patch.
-
-First we need to create a temporary new branch for these changes and
-switch into it:
-
-  % git checkout -b experimental
-
-Patches that were formatted by C<git format-patch> are applied with
-C<git am>:
-
-  % git am 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
-  Applying Rename Leon Brocard to Orange Brocard
-
-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.
-
-=head1 Cleaning a working directory
-
-The command C<git clean> can with varying arguments be used as a
-replacement for C<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 C<git
-checkout> and give it a list of files to be reverted, or C<git checkout
--f> to revert them all.
-
-If you want to cancel one or several commits, you can use C<git reset>.
-
-=head1 Bisecting
-
-C<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 F<~/testcase.pl> that exits with C<0>
-when some behaviour is correct, and with C<1> when it's faulty. You
-need an helper script that automates building C<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.
-  git show blead:makedepend.SH > makedepend.SH
-
-  # If you can use ccache, add -Dcc=ccache\ gcc -Dld=gcc to the Configure line
-  # if Encode is not needed for the test, you can speed up the bisect by
-  # excluding it from the runs with -Dnoextensions=Encode
-  sh Configure -des -Dusedevel -Doptimize="-g"
-  test -f config.sh || exit 125
-  # Correct makefile for newer GNU gcc
-  perl -ni -we 'print unless /<(?:built-in|command)/' makefile x2p/makefile
-  # if you just need miniperl, replace test_prep with miniperl
-  make test_prep
-  [ -x ./perl ] || exit 125
-  ./perl -Ilib ~/testcase.pl
-  ret=$?
-  [ $ret -gt 127 ] && ret=127
-  # git checkout makedepend.SH
-  git clean -dxf
-  exit $ret
-
-This script may return C<125> to indicate that the corresponding commit
-should be skipped. Otherwise, it returns the status of
-F<~/testcase.pl>.
-
-You first enter in bisect mode with:
-
-  % git bisect start
-
-For example, if the bug is present on C<HEAD> but wasn't in 5.10.0,
-C<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 C<HEAD> and
-C<perl-5.10.0>. You can then run the bisecting process with:
-
-  % git bisect run ~/run
-
-When the first bad commit is isolated, C<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 C<git bisect log> and
-C<git bisect visualize>. C<git bisect reset> will get you out of bisect
-mode.
-
-Please note that the first C<good> state must be an ancestor of the
-first C<bad> state. If you want to search for the commit that I<solved>
-some bug, you have to negate your test case (i.e. exit with C<1> if OK
-and C<0> if not) and still mark the lower bound as C<good> and the
-upper as C<bad>. The "first bad commit" has then to be understood as
-the "first commit where the bug is solved".
-
-C<git help bisect> has much more information on how you can tweak your
-binary searches.
-
-=head1 Submitting a patch via GitHub
-
-GitHub is a website that makes it easy to fork and publish projects
-with Git. First you should set up a GitHub account and log in.
-
-Perl's git repository is mirrored on GitHub at this page:
-
-  http://github.com/mirrors/perl/tree/blead
-
-Visit the page and click the "fork" button. This clones the Perl git
-repository for you and provides you with "Your Clone URL" from which
-you should clone:
-
-  % git clone git@github.com:USERNAME/perl.git perl-github
-
-The same patch as above, using github might look like this:
-
-  % cd perl-github
-  % git remote add upstream git://perl5.git.perl.org/perl.git
-  % git pull upstream blead
-  % git checkout -b orange
-  % perl -pi -e 's{Leon Brocard}{Orange Brocard}' AUTHORS
-  % git commit -a -m 'Rename Leon Brocard to Orange Brocard'
-  % git push origin orange
-
-The orange branch has been pushed to GitHub, so you should now send an
-email (see L</Submitting a patch>) with a description of your changes
-and the following information:
-
-  http://github.com/USERNAME/perl/tree/orange
-  git://github.com/USERNAME/perl.git branch orange
-
-=head1 Merging from a branch via GitHub
-
-If someone has provided a branch via GitHub and you are a committer,
-you should use the following in your perl-ssh directory:
-
-  % 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 you can see the commits:
-
-  % git log avar/orange
-
-If you approve of a specific commit, you can cherry pick it:
-
-  % git cherry-pick 0c24b290ae02b2ab3304f51d5e11e85eb3659eae
-
-Or you could just merge the whole branch if you like it all:
-
-  % git merge avar/orange
-
-And then push back to the repository:
-
-  % git push
-
-
-=head1 Topic branches and rewriting history
-
-Individual committers should create topic branches under
-B<yourname>/B<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 B<yourname>/B<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 C<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
-
-B<NOTE:> it is forbidden at the repository level to delete any of the
-"primary" branches. That is any branch matching
-C<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 B<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.)
-
-=head1 Committing to blead
-
-If you are a committer, you have the right to commit changes directly to
-the 'blead' branch, which will become the next production release of Perl.
-
-Before pushing I<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:
-
-=over
-
-=item *
-
-Make sure you have a good commit message. See L</Commit message> elsewhere in
-this document
-
-=item *
-
-Run the test suite.  You might not think that one typo fix would break
-a test file. You'd be wrong.  Here's an example of where not running the
-suite caused problems.  A patch was submitted that added a couple of
-tests to an existing .t.  It couldn't possibly affect anything else, so
-no need to test beyond the single affected .t, right?  But, the
-submitter's email address had changed since the last of their
-submissions, and this caused other tests to fail.  Running the test
-target given in the next item would have caught this problem.
-
-=item *
-
-If you don't run the full test suite, at least C<make test_porting>.
-This will run basic sanity checks. To see which sanity checks, have a
-look in F<t/porting>.
-
-=back
-
-=head1 Committing to maintenance versions
-
-Maintenance versions should only be altered to add critical bug fixes,
-see L<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 C<maint-5.005>, which tracks the
-remote branch C<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 C<git cherry-pick> command. It is recommended to use the
-B<-x> option to C<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 L</Committing to blead> above.
-
-=head1 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
-C<.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.
-
-=head1 SEE ALSO
-
-=over
-
-=item *
-
-The git documentation, accessible via the C<git help> command
-
-=item *
-
-L<perlpolicy> - Perl core development policy
-
-=back
-
-=cut