git-graft and git-find brainstorm

[ link: git-graft-brainstorm | tags: git git-find git-graft | updated: Tue, 29 Aug 2006 14:11:42 ]

I want to be able to take a bunch of patches that were applied to one semi-related branch and appened them to the current branch, or better yet a new branch of the current. The bunch of patches will be selected by what they change; I should be able to graft all patches that modify some file, or modify some regular expression.

Here is what I mean:

 ,-----X---X---X---X--- ... ---             "historical" branch
o
 `--------------------Y                     "current" branch
                       \
                        `---Z---Z---...     "working" branch

You start off at current branch and run something like:

git-find historical --file some_file.c --or --re 'some pattern' \
| git-graft --new-branch working -

This will let me take the interesting subset of X commits and apply them at some point Y. Should the patches X cause conflicts with the current branch, then git-graft needs to let the user resolve those conflicts a patch at a time. The default is to apply onto the current branch, however if desired it should be possible to create the changes on a new, working, branch. The result is a new set of Z commits, as shown above.

There are two commands here: git-find and git-graft. Starting with git-find; here is what I would like it to support initially:

git-find <commits> <match-condition>

git-find searches the commits in a specified range and returns
those commits that modify the repository in a specific way.

The commits to start with can be represented in a few ways:

    <A>                    - all commits from <A> to HEAD
    <A> <B> ...            - individual commits listed
    <A>..<B>               - all commits in given range
    -                      - list of commit hashes from stdin

The match criteria can be defined using a grammar similar to
the find command.  The following are supported match conditions:

    --file <glob>          - match on this file pattern
    --re <reg-exp>         - match diffs that contain this change

To separate the match conditions use the following

    ( <condition>... )     - group together match conditions
    --or                   - boolean or
    --and                  - boolean and

I would also like it to search for things in the commit message, like --author, --date, --desc, --signed, etc. But that can be added later.

The second tool I need is git-graft; this tool lets you cherry pick a slew of patches from one branch to the other. Initially I wanted to have git-graft just pick a range of, like all the X'es above, and "graft" them onto a new branch. However, my current usecase requires that something selects the changesets I want and append that onto a branch.

This sounds very familiar. That's kinda what git-cherry-pick does, but for one commit. So I have to make a choice:

I can build git-graft ontop of git-cherry-pick and add statefullness to it the way that git-rebase works, or
I can extend the way that git-cherry-pick works and make it accept a range of commits to appply and add statefullness to it.

I think I will start with the first approach and then have the git maintainers decide. So, now back to git-graft...

git-graft operates in a similar way to git-rebase, except that git-rebase is too rigid. It's possible to implement git-rebase on top of git-graft. Here is what I want to see:

git-rebase <options> <commits>

git-rebase takes a range of commits and applies them one-by-one
onto a branch.  If a patch does noe cleanly apply, git-rebase will
stop and allow the user to resolve any conflicts and continue.

Branching control:

    -b --new-branch <new-branch>
                           - create and checkout a new branch 
                             before applying patches
    --branch-from <existing-branch>
                           - <new-branch> is created from an
                             <existing-branch>
Commits to apply:

    <A>                    - apply all commits from <A> to HEAD
    <A> <B> ...            - apply individual commits listed
    <A>..<B>               - apply all commits in given range
    -                      - read list of commit hashes from stdin

... now off to write some code.

Bart's Blog

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I am an embedded Linux software developer and consultant operating under Jukie Networks Inc in Ottawa, Canada.