Re: rev-list --cherry-pick and context lines

[Michael J Gruber <git@drmicha.warpmail.net>]

Stefan Haller venit, vidit, dixit 02.09.2011 12:35:
> Consider two commits on different branches, one with this patch:
> 
>     diff --git a/file.txt b/file.txt
>     index 704fa27..2f7e74c 100644
>     --- a/file.txt
>     +++ b/file.txt
>     @@ -1,3 +1,3 @@
>      old_context
>      
>     -foo
>     +bar
> 
> and the other with this patch:
> 
>     diff --git a/file.txt b/file.txt
>     index f35051b..8c7de32 100644
>     --- a/file.txt
>     +++ b/file.txt
>     @@ -1,3 +1,3 @@
>      new_context
>      
>     -foo
>     +bar
> 
> If I run "git rev-list --cherry-pick --left-right branch1...branch2", it
> reports both commits as being genuine commits on their respective
> branch, even though I consider their patches to be the same.
> 
> I guess for my purpose I would like to have patch-ids that ignore
> context (or that use only one line of context, I'm not sure which).
> 
> In fact, if I do "git show <commit> -U1 | git patch-id", both commits
> show the same id.
> 
> So, would it make sense to have a parameter for git-rev-list (and
> git-cherry) that lets you specify how much context to be used for the
> patch ids?

It would be a bit like the patch below. "git log" accepts diff options already.
But:

- Do we want the patch id generation and the patch display (-p) to use the
  same options?

- -U1 implies -p/--patch and there is no --no-patch.

- Which other diff options do we want to pass to the patch id
  generation: --histogram, --patience, ...?

Cheers,
Michael

----

diff --git i/diff.c w/diff.c
index fcc0078..4e82912 100644
--- i/diff.c
+++ w/diff.c
@@ -4103,7 +4103,7 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 		}
 
 		xpp.flags = 0;
-		xecfg.ctxlen = 3;
+		xecfg.ctxlen = options->context;
 		xecfg.flags = 0;
 		xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
 			      &xpp, &xecfg);
diff --git i/revision.c w/revision.c
index 072ddac..5a98ed9 100644
--- i/revision.c
+++ w/revision.c
@@ -601,6 +601,7 @@ static void cherry_pick_list(struct commit_list *list, struct rev_info *revs)
 	left_first = left_count < right_count;
 	init_patch_ids(&ids);
 	ids.diffopts.pathspec = revs->diffopt.pathspec;
+	ids.diffopts.context = revs->diffopt.context;
 
 	/* Compute patch-ids for one side */
 	for (p = list; p; p = p->next) {