=head1 NAME 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 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 master 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 this over the web. This allows you to browse the tree, see recent commits, search for particular commits and more. You may access it at: http://perl5.git.perl.org/perl.git =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 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 slower): git clone http://perl5.git.perl.org/perl.git perl-http This clones the repository and makes a local copy in the F 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/gitroot/perl.git perl-ssh 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: [remote "origin"] url = git://perl5.git.perl.org/perl.git 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. 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 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, which is faster and doesn't require you to authenticate, and to push your changes back with the C remote: % git fetch camel % git push camel The C command just updates the C refs, as the objects themselves should have been fetched when pulling from C. =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 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 which will be configured to merge from the remote tracking branch C. 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 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 switch to another branch: % git checkout origin/maint-5.8-dor 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 ..." to unstage) # # modified: pod/perlrepository.pod # # Changed but not updated: # (use "git add ..." to update what will be committed) # # modified: pod/perlrepository.pod # # Untracked files: # (use "git add ..." 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 which has not been pushed to the C remote yet. B: that this output is also what you see as a template if you do not provide a message to C. Assuming we commit all the mentioned changes above: % git commit -a -m'explain git status and stuff about remotes' Created commit daf8e63: explain git status and stuff about remotes 1 files changed, 83 insertions(+), 3 deletions(-) We can re-run git status and see something like this: % git status # On branch blead # Your branch is ahead of 'origin/blead' by 2 commits. # # Untracked files: # (use "git add ..." 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 branch, and your repository is up to date: % git checkout blead % git pull (It's preferable to patch against the latest blead version, since patches are usually integrated from blead to the maintenance branches. This does not apply, obviously, in the rare case where your patch is specific to a maintaince release.) 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 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 ..." 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 Laszlo Molnar Leif Huhn Len Johnson -Leon Brocard +Orange Brocard Les Peters Lesley Binks Lincoln D. Stein Now commit your change locally: % git add AUTHORS % git commit -m 'Rename Leon Brocard to Orange Brocard' Created commit 6196c1d: Rename Leon Brocard to Orange Brocard 1 files changed, 1 insertions(+), 1 deletions(-) Now you should create a patch file for all your local changes: % git format-patch origin 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch You should now send an email to perl5-porters@perl.org with a description of your changes, and attach this patch file as an attachment. 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 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 C. =head2 A note on binary files Since the patch(1) utility cannot deal with binary files, it's important that you either avoid the use of binary files in your patch, generate the files dynamically, or that you encode any binary files using the F utility. Assuming you needed to include a gzip-encoded file for a module's test suite, you might do this as follows using the F utility: $ perl uupacktool.pl -v -p -D lib/Some/Module/t/src/t.gz Writing lib/Some/Module/t/src/t.gz into lib/Some/Module/t/src/t.gz.packed This will replace the C file with an encoded counterpart. During C, before any tests are run, perl's Makefile will restore all the C<.packed> files mentioned in the MANIFEST to their original name. This means that the test suite does not need to be aware of this packing scheme and will not need to be altered. =head2 Getting your patch accepted The first thing you should include with your patch is a description of the problem that the patch corrects. If it is a code patch (rather than a documentation patch) you should also include a small test case that illustrates the bug (a patch to an existing test file is preferred). If you are submitting a code patch there are several other things that you need to do. =over 4 =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 When submitting a patch you should make every effort to also include an addition to perl's regression tests to properly exercise your patch. Your testsuite additions should generally follow these guidelines (courtesy of Gurusamy Sarathy ): 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 are applied with C: % 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 " Now we can inspect the change: % git log commit b1b3dab48344cff6de4087efca3dbd63548ab5e2 Author: Leon Brocard Date: Fri Dec 19 17:02:59 2008 +0000 Rename Leon Brocard to Orange Brocard ... % git diff blead diff --git a/AUTHORS b/AUTHORS index 293dd70..722c93e 100644 --- a/AUTHORS +++ b/AUTHORS @@ -541,7 +541,7 @@ Lars Hecking Laszlo Molnar Leif Huhn Len Johnson -Leon Brocard +Orange Brocard Les Peters Lesley Binks Lincoln D. Stein 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 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 C and give it a list of files to be reverted. If you want to cancel one or several commits, you can use C. =head1 BISECTING C 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 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 but wasn't in 5.10.0, C 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 and C. We can then run the bisecting process with: % git bisect run ~/run When the first bad commit is isolated, C will tell you so: ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5 is first bad commit commit ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5 Author: Dave Mitchell 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 and C. C will get you out of bisect mode. Please note that the first C state must be an ancestor of the first C state. If you want to search for the commit that I 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 and the upper as C. The "first bad commit" has then to be understood as the "first commit where the bug is solved". C has much more information on how you can tweak your binary searches. =head1 COMMITTING 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 C, which tracks the remote branch C. 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 command. It is recommended to use the B<-x> option to C in order to record the SHA1 of the original commit in the new commit message. =head1 SEE ALSO The git documentation, accessible via C.