Merge branch 'blead' of nicholas@perl5.git.perl.org:/gitroot/perl into blead

1 files changed, 145 insertions, 54 deletions

diff --git a/pod/perlrepository.pod b/pod/perlrepository.pod
index 56e61f14a4..4c2a7c9926 100644
--- a/pod/perlrepository.pod
+++ b/pod/perlrepository.pod
@@ -5,8 +5,8 @@ perlrepository - Using the Perl source repository
 =head1 SYNOPSIS
 
 All of Perl's source code is kept centrally in a Git repository. The
-repository contains many Perl revisions from Perl 1 onwards and all
-the revisions from Perforce, the version control system we were using
+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
@@ -45,8 +45,8 @@ 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:
+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/gitroot/perl.git perl-ssh
 
@@ -54,8 +54,8 @@ This clones the repository and makes a local copy in the 'perl-ssh'
 directory.
 
 If you clone using git, which is faster than ssh, then you will need to
-modify your config in order to enable pushing. Edit F<.git/config> where
-you will see something like:
+modify your config in order to enable pushing. Edit F<.git/config>
+where you will see something like:
 
   [remote "origin"]
   url = git://perl5.git.perl.org/perl.git
@@ -65,27 +65,33 @@ change that to something like this:
   [remote "origin"]
   url = ssh://perl5.git.perl.org/gitroot/perl.git
 
-NOTE: there are symlinks set up so that the /gitroot is actually optional.
+NOTE: there are symlinks set up so that the /gitroot is actually
+optional.
 
 You can also set up your user name and e-mail address. For example
 
   % git config user.name "Leon Brocard"
   % git config user.email acme@astray.com
 
-It is also possible to keep C<origin> as a git remote, and add a new remote for ssh access:
+It is also possible to keep C<origin> as a git remote, and add a new
+remote for ssh access:
 
   % git remote add camel user@camel:/gitroot/perl.git
 
-This allows you to update your local repository by pulling from C<origin>, which is faster and doesn't require you to authentify, and to push your changes back with the C<camel> remote:
+This allows you to update your local repository by pulling from
+C<origin>, which is faster and doesn't require you to authentify, 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>.
+The C<fetch> command just updates the C<camel> refs, as the objects
+themselves should have been fetched when pulling from C<origin>.
 
 =head1 OVERVIEW OF THE REPOSITORY
 
-Once you have changed into the repository directory, you can inspect it.
+Once you have changed into the repository directory, you can inspect
+it.
 
 
 After a clone the repository will contain a single local branch, which
@@ -94,8 +100,8 @@ will be the current branch as well, as indicated by the asterix.
   % git branch
   * blead
 
-Using the -a switch to branch will also show the remote tracking branches in the
-repository:
+Using the -a switch to branch will also show the remote tracking
+branches in the repository:
 
   % git branch -a
   * blead
@@ -103,42 +109,43 @@ repository:
     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>.
+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)
+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:
+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:
+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
+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.
+Neither of these last two commands will update your working directory,
+however both will update the remote-tracking branches in your
+repository.
 
 To switch to another branch:
 
@@ -158,11 +165,11 @@ 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:
+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
@@ -183,13 +190,14 @@ following:
   #
   #       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>.
+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 we commit all the mentioned changes above:
 
@@ -210,8 +218,9 @@ We can re-run git status and see something like this:
   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.
+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
 
@@ -224,15 +233,14 @@ 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:
+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
 
-Now that we have everything up to date, we need to create a temporary new
-branch for these changes and switch into it:
+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
 
@@ -308,11 +316,18 @@ switch into it:
 
   % git checkout -b experimental
 
-Now we should apply the patch:
+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 -am "Some fixing" --author="That Guy <that.guy@internets.com>"
+
 Now we can inspect the change:
 
   % git log
@@ -356,7 +371,8 @@ If you want to delete your temporary branch, you may do so with:
 
 =head1 CLEANING A WORKING DIRECTORY
 
-The command C<git clean> can with varying arguments be used as a replacement for make-clean.
+The command C<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:
 
@@ -366,6 +382,81 @@ 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.
+to remove all ignored untracked files, such as build and test
+byproduct, but leave any  manually created files alone.
+
+=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. We need
+an helper script that automates building C<perl> and running the
+testcase:
+
+  % cat ~/run
+  #!/bin/sh
+  git clean -dxf
+  # If you can use ccache, add -Dcc=ccache\ gcc -Dld=gcc to the Configure line
+  sh Configure -des -Dusedevel -Doptimize="-g" || exit 125
+  make || exit 125
+  ./perl -Ilib ~/testcase.pl
+
+This script may return C<125> to indicate that the corresponding commit
+should be skipped. Otherwise, it returns the status of
+F<~/testcase.pl>.
+
+We 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>. We 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 + Unkown 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 COMITTING TO MAINTENANCE VERSIONS
+
+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.