non-regression bug in 'git merge' (really, xdiff/xmerge, I think)

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 2, 2020, 22:21 UTC
Message-ID: <xmqqy2si9z4x.fsf_-_@gitster-ct.c.googlers.com>
In-Reply-To: <20200302181924.GB1571684@cat>

Thomas Gummerer <t.gummerer@gmail.com> writes:

Show 12 quoted lines

> diff --git a/Makefile b/Makefile
> index 9804a0758b..096c6d1fbb 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -609,7 +609,6 @@ SCRIPT_SH += git-merge-one-file.sh
>  SCRIPT_SH += git-merge-resolve.sh
>  SCRIPT_SH += git-mergetool.sh
>  SCRIPT_SH += git-quiltimport.sh
> -SCRIPT_SH += git-legacy-stash.sh
>  SCRIPT_SH += git-request-pull.sh
>  SCRIPT_SH += git-submodule.sh
>  SCRIPT_SH += git-web--browse.sh

Merging this topic to 'pu', which has dl/merge-autostash topic already merged, breaks the build and it is not fault of Thomas's topic. dl/merge-autostash has the following bit:

commit 4b981afaa03c00524f1d4986271a3f4cc119f4cd
Merge: 06928448f7 de4db86ff2
Author: Junio C Hamano <gitster@pobox.com>
Date:   Mon Mar 2 13:23:26 2020 -0800

    Merge branch 'dl/merge-autostash' into pu
    
    "git merge" learns the "--autostash" option.
    
    * dl/merge-autostash:
      ...
      Makefile: alphabetically sort += lists

diff --git a/Makefile b/Makefile
index a5961113d8..c0793ac75b 100644
--- a/Makefile
+++ b/Makefile
@@ -604,12 +604,12 @@ unexport CDPATH
 SCRIPT_SH += git-bisect.sh
 SCRIPT_SH += git-difftool--helper.sh
 SCRIPT_SH += git-filter-branch.sh
+SCRIPT_SH += git-legacy-stash.sh
 SCRIPT_SH += git-merge-octopus.sh
 SCRIPT_SH += git-merge-one-file.sh
 SCRIPT_SH += git-merge-resolve.sh
 SCRIPT_SH += git-mergetool.sh
 SCRIPT_SH += git-quiltimport.sh
-SCRIPT_SH += git-legacy-stash.sh
 SCRIPT_SH += git-request-pull.sh
 SCRIPT_SH += git-submodule.sh
 SCRIPT_SH += git-web--browse.sh
@@ -617,8 +617,8 @@ SCRIPT_SH += git-web--browse.sh

which makes it appear to the xmerge code that legacy-status that
used to exist in between quiltimport and request-pull has already
been removed.

As Thomas's above patch exactly wants to do that (i.e. we want to
remove legacy-stash between quiltimport and request-pull), the
xmerge code seems to think incorrectly that the requested change has
already been applied.  And as a result of that, there remains
legacy-stash between fliter-branch and merge-octopus, breaking the
build by having one unbuildable build target X-<.