[PATCH v6 0/2] merge-tree: allow specifying a base commit when --write-tree is passed

Thanks for Elijah's work. I'm very excited that merge-ort is integrated into the git merge-tree, which means that we can use merge-ort in bare repositories to optimize merge performance.

In this patch, I introduce a new --merge-base=<commit> option to allow callers to specify a merge-base for the merge. This may allow users to implement git cherry-pick and git rebase in bare repositories with git merge-tree cmd.

Changes since v1:

 * Changed merge_incore_recursive() to merge_incore_nonrecursive() when
   merge-base is specified.
 * Fixed c style problem.
 * Moved commit lookup/die logic out to the parsing logic in
   cmd_merge_tree().
 * use test_commit for test

Changes since v2:

 * commit message
 * Rebased on top of en/merge-tree-sequence.
 * Set opt.ancestor to o->merge_base. Because opt.ancestor is a *char. To
   make it easier to pass parameters, I moved
   lookup_commit_reference_by_name() to real_ merge() again.
 * Added test comment.

Changes since v3:

 * support --merge-base in conjunction with --stdin

Changes since v4:

 * commit message
 * added input format document
 * changed the input format for specifying the merge-base when --stdin is
   passed
 * changed the output when --stdin and --merge-base are used at the same
   time
 * add comment for test

Changes since v5:

 * improved test: remove the test repo after the test; avoid sub-shell.

Kyle Zhao (2):
  merge-tree.c: add --merge-base=<commit> option
  merge-tree.c: allow specifying the merge-base when --stdin is passed

 Documentation/git-merge-tree.txt | 16 ++++++++
 builtin/merge-tree.c             | 65 ++++++++++++++++++++++++++------
 t/t4301-merge-tree-write-tree.sh | 61 ++++++++++++++++++++++++++++++
 3 files changed, 130 insertions(+), 12 deletions(-)

base-commit: ec1edbcb56ac05e9980299b05924c5c1b51d68b4
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1397%2Fkeyu98%2Fkz%2Fmerge-tree-option-merge-base-v6
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1397/keyu98/kz/merge-tree-option-merge-base-v6
Pull-Request: https://github.com/gitgitgadget/git/pull/1397

Range-diff vs v5:

 1:  01df0d1a6a7 ! 1:  1cf1c69b8e8 merge-tree.c: add --merge-base=<commit> option
     @@ t/t4301-merge-tree-write-tree.sh: test_expect_success '--stdin with both a succe
      +
      +test_expect_success 'specify merge-base as parent of branch2' '
      +	# Setup
     -+	git init base-b2-p && (
     -+		cd base-b2-p &&
     -+		test_commit c1 file1 &&
     -+		test_commit c2 file2 &&
     -+		test_commit c3 file3
     -+	) &&
     ++	test_when_finished "rm -rf base-b2-p" &&
     ++	git init base-b2-p &&
     ++	test_commit -C base-b2-p c1 file1 &&
     ++	test_commit -C base-b2-p c2 file2 &&
     ++	test_commit -C base-b2-p c3 file3 &&
     ++
      +	# Testing
     -+	(
     -+		cd base-b2-p &&
     -+		TREE_OID=$(git merge-tree --write-tree --merge-base=c2 c1 c3) &&
     ++	TREE_OID=$(git -C base-b2-p merge-tree --write-tree --merge-base=c2 c1 c3) &&
      +
     -+		q_to_tab <<-EOF >expect &&
     -+		100644 blob $(git rev-parse c1:file1)Qfile1
     -+		100644 blob $(git rev-parse c3:file3)Qfile3
     -+		EOF
     ++	q_to_tab <<-EOF >expect &&
     ++	100644 blob $(git -C base-b2-p rev-parse c1:file1)Qfile1
     ++	100644 blob $(git -C base-b2-p rev-parse c3:file3)Qfile3
     ++	EOF
      +
     -+		git ls-tree $TREE_OID >actual &&
     -+		test_cmp expect actual
     -+	)
     ++	git -C base-b2-p ls-tree $TREE_OID >actual &&
     ++	test_cmp expect actual
      +'
      +
       test_done
 2:  3bdfad03cca ! 2:  40d56544e6e merge-tree.c: allow specifying the merge-base when --stdin is passed
     @@ t/t4301-merge-tree-write-tree.sh: test_expect_success '--stdin with both a succe
       # git merge-tree --write-tree --merge-base=c2 c1 c3
       #   Commit c1: add file1
      @@ t/t4301-merge-tree-write-tree.sh: test_expect_success 'specify merge-base as parent of branch2' '
     - 	)
     + 	test_cmp expect actual
       '
       
      +# Since the earlier tests have verified that individual merge-tree calls
      +# are doing the right thing, this test case is only used to test whether
      +# the input format is available.
      +
     -+test_expect_success '--stdin with both a normal merge and a merge-base specified merge' '
     -+	cd base-b2-p &&
     -+	printf "c1 c3\nc2 -- c1 c3" | git merge-tree --stdin >actual &&
     ++test_expect_success 'check the input format when --stdin is passed' '
     ++	test_when_finished "rm -rf repo" &&
     ++	git init repo &&
     ++	test_commit -C repo c1 &&
     ++	test_commit -C repo c2 &&
     ++	test_commit -C repo c3 &&
     ++	printf "c1 c3\nc2 -- c1 c3\nc2 c3" | git -C repo merge-tree --stdin >actual &&
      +
      +	printf "1\0" >expect &&
     -+	git merge-tree --write-tree -z c1 c3 >>expect &&
     ++	git -C repo merge-tree --write-tree -z c1 c3 >>expect &&
      +	printf "\0" >>expect &&
      +
      +	printf "1\0" >>expect &&
     -+	git merge-tree --write-tree -z --merge-base=c2 c1 c3 >>expect &&
     ++	git -C repo merge-tree --write-tree -z --merge-base=c2 c1 c3 >>expect &&
      +	printf "\0" >>expect &&
     ++
     ++	printf "1\0" >>expect &&
     ++	git -C repo merge-tree --write-tree -z c2 c3 >>expect &&
     ++	printf "\0" >>expect &&
     ++
      +	test_cmp expect actual
      +'
      +