Hi Michael
On 20/12/2023 06:51, Michael Lohmann wrote:
Hi Phillip
On 18/12/2023 16:42, Phillip Wood wrote:
Thanks for bringing this up I agree it can be very helpful to look at
the original commit when resolving cherry-pick and revert conflicts.
As an aside I find it useful is to do a kind of range-diff before
committing the conflict resolution. Unfortunately one cannot use "git
range-diff" because the conflict resolution is not yet committed.
Instead I use
diff <(git diff CHERRY_PICK_HEAD^-) <(git diff HEAD)
in practice it is helpful to pipe the diffs through sed to delete the
"index" lines and normalize the hunk headers.
I'm in two minds about this change though - I wonder if it'd be better
to improve the documentation for CHERRY_PICK_HEAD and REVERT_HEAD and
tell users to run "git show CHERRY_PICK_HEAD" instead. I think the
main reason we have a "--show-current-patch" option for "rebase" is
that there are two different implementations of that command and the
patched-based one of them does not support REBASE_HEAD. That reasoning
does not apply to "cherry-pick" and "revert" and
"--show-current-patch" suggests a patch-based implementation which is
also not the case for these commands.
I appreciate the urge of limiting the interface to the minimum needed
and not to duplicate functionality that already exists. On the other
hand, this would
a) grant the user the same experience, not having to wonder about
implementation details such as different backends for rebase, but not
for revert/cherry-pick and
b) (I know it is more indicative of me, but:) when I am looking for a
feature in software and I look into the respective man page I tend to
focus first on the synopsis instead of reading the whole page (or
sometimes I even just rely on the shell autocompletion for
discoverability).
So yes, mentioning REVERT_HEAD and CHERRY_PICK_HEAD in the respective
docs would technically be sufficient, but I don't think it is as
discoverable to an average user (who does not know about the details of
all the existing pseudo refs) as a toplevel action would be. But an
assessment of the pros and cons is not on me to decide.
To make the psuedo refs discoverable we should certainly be mentioning
them in the section about resolving conflicts. I haven't checked what
the docs say at the moment but a worked example showing how to inspect
the conflicts and the original changes would be helpful I think. That
does assume that the user actually reads the section about resolving
conflicts rather than just scanning the available command line options
though.
I have to be honest: I have troubles distinguishing a "patch" and a
"diff", the latter of which `git show <commit>` shows according to the
documentation ("For commits it shows the log message and textual
diff."), though my understanding was that a patch is a diff + context
lines, which is what `git show` actually shows... I think this is
probably why I don't feel so strong about the potential loose usage of
the word here.
I think for the purposes of this discussion "patch" and "diff" are
largely interchangeable (a "patch" is essentially a "diff" with a commit
message). Maybe I'm overthinking it but the reason I'm not very keen on
"--show-current-patch" (in addition to the "duplicate functionality"
argument you mention above) is that cherry-pick and revert do not work
by applying patches (or diffs) but use a 3-way merge instead. I think
--show-current-patch first appeared as an option to "git am" which makes
sense as that command is all about applying patches.
I'd be interested to hear what other people think about whether it makes
"--show-current-patch" make sense for other commands.
Also the documentation of cherry-pick already uses the word "patch" in a
(according to my understanding from a technical perspective) sloppy (but
from a layman's point of view probably nevertheless helpful) way:
The following sequence attempts to backport a patch, bails out because
the code the patch applies to has changed too much, and then tries
again, this time exercising more care about matching up context lines.
------------
$ git cherry-pick topic^ <1>
$ git diff <2>
$ git cherry-pick --abort <3>
$ git cherry-pick -Xpatience topic^ <4>
------------
<1> apply the change that would be shown by `git show topic^`.
In this example, the patch does not apply cleanly, so
information about the conflict is written to the index and
working tree and no new commit results.
Should that also be rephrased?
It would certainly be more accurate for the first paragraph to say
something like
The following sequence tries to backport a commit. It bails out
because the code modified by the commit has conflicting changes in
the current branch.
The bit about exercising more care about matching up context lines is
moot these days as the default merge strategy is "ort" which uses the
histogram diff algorithm to do just that so commands <3> & <4> should
not be needed.
Out of curiosity: The following from the rebase docs seems to imply that
the apply backend will probably be removed in the future:
--apply
Use applying strategies to rebase (calling git-am
internally). This option may become a no-op in the future
once the merge backend handles everything the apply one
does.
But I would expect the `rebase --show-current-patch` still to be
working. Would that only be a legacy compatibility flag and instead also
for rebases the recommended option would be to run
`git show REBASE_HEAD`?
The long term goal is to remove the apply backend but I don't think
anyone is actively working on it at the moment. We'd certainly need to
keep the --show-current-patch option for backwards compatibility.
I'll be off the list for the next couple of weeks but I'll be sure to
catch up with this thread in the New Year
Best Wishes
Phillip
