Re: GSoC idea: allow "git rebase --interactive" todo lines to take options

[Michael Haggerty <mhagger@alum.mit.edu>]

On 02/26/2014 11:52 AM, Jeff King wrote:
> On Wed, Feb 26, 2014 at 09:04:30AM +0100, Michael Haggerty wrote:
> 
>> It would be nice to support more flexibility in the todo-list commands
>> by allowing the commands to take options.  Maybe
>>
>> * Convert a commit into a merge commit:
>>
>>       pick -p c0ffeee -p e1ee712 deadbab The oneline of the commit after
> 
> This seems like a reasonable feature to me. All of your examples are
> possible with an "e"dit and another git command, but the convenience may
> be worth it (though personally, most of the examples you gave are
> particularly interesting to me[1]).
> 
> I'd worry a little that it is not a summer's worth of work, but I
> suspect there are other parts of rebase--interactive that could use
> attention once the student is familiar with the code.
> 
>> * After squashing two commits, add a "Signed-off-by" line to the
>>   commit log message:
>>
>>     pick deadbee Implement feature XXX
>>     squash --signoff f1a5c00 Fix to feature XXX
>>
>>   or GPG-sign a commit:
>>
>>     pick --gpg-sign=<keyid> deadbee Implement feature XXX
>>
>> * Reset the author of the commit to the current user or a specified
>>   user:
>>
>>     pick --reset-author deadbee Implement feature XXX
>>     pick --author="A U Thor <author@example.com>" deadbab The oneline of
>> the commit after
> 
> Your first example would need some commit-tree magic, I think. But could
> you implement these two with:
> 
>    pick deadbee Implement feature XXX
>    exec git commit --amend --signoff --reset-author
> 
> ? You could even alias the "amend" command to "exec git commit --amend",
> like:
> 
>   amend --signoff --reset-author
> 
> Maybe that is unnecessarily unfriendly to the user, though.

The whole point is to make these things easy.  But I have to admit that
"amend" would be another nice todo-list command.  Once the
infrastructure is there to handle options, it would be no big deal to
add an "amend" command with a "--signoff" option and offer the same
"--signoff" option on other, existing commands.

> [1] The one feature I would like in this vein is that editing the title
>     in the instruction-sheet would modify the commit message of the
>     relevant commit. For some reason I try to do this every few weeks,
>     but of course the changes are just thrown away.

Given that commit messages can be more than one line long, a feature
like this would be confusing, I think, and perhaps subtly encourage
people to limit their commit messages to a single line, which would be a
bad thing.  Plus, until now such edits were thrown away, so there are
backwards compatibility problems if we suddenly start preserving such edits.

But using the other ideas discussed here one could do

    pick -m "New log message" <sha1>

or

    amend -m "Revised log message"

It also might be reasonable, if the user edits the title in a way that
does not simply delete characters at the end, to do an implicit "reword"
with the edited title stuck in at the first line (and maybe the original
title following it, commented out with "#").

Another, more wonkish idea I though of would be

    pick --tree=<treeish> <sha1>

to force the tree of the commit to be set to that of the specified
<treeish> while keeping the commit metadata from <sha1>.  What would
this be useful for?  When swapping two commits, it is often the case
that conflicts have to be resolved twice.  But the tree should be the
same after both commits are applied, regardless of the order in which
they are applied.  So one could change

    pick aaaaaaa
    pick bbbbbbb

to

    pick bbbbbbb
    pick --tree=bbbbbbb aaaaaaa

On the other hand, maybe "git rebase --interactive" should have the
intelligence to do this automatically whenever the set of commits
pre/post rewriting is identical, possibly if a "--reorder-only" option
is used.

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/