[PATCH v7 0/2] merge-tree: allow specifying a base commit when --write-tree is passed

Thanks for everyone's careful reviews.

In this patch, I introduce a new --merge-base=<commit> option to allow callers to specify a merge-base for the merge and extend the input accepted by --stdin to also allow a specified merge-base with each merge requested.

Regards, Kyle

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.

Changes since v6:

 * fixed comment of test

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 | 62 ++++++++++++++++++++++++++++++
 3 files changed, 131 insertions(+), 12 deletions(-)

base-commit: ec1edbcb56ac05e9980299b05924c5c1b51d68b4
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1397%2Fkeyu98%2Fkz%2Fmerge-tree-option-merge-base-v7
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1397/keyu98/kz/merge-tree-option-merge-base-v7
Pull-Request: https://github.com/gitgitgadget/git/pull/1397

Range-diff vs v6:

 1:  1cf1c69b8e8 = 1:  1cf1c69b8e8 merge-tree.c: add --merge-base=<commit> option
 2:  40d56544e6e ! 2:  48e55d4e97c merge-tree.c: allow specifying the merge-base when --stdin is passed
     @@ t/t4301-merge-tree-write-tree.sh: test_expect_success 'specify merge-base as par
       '
       
      +# 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.
     ++# are doing the right thing, this test case is only used to verify that
     ++# we can also trigger merges via --stdin, and that when we do we get
     ++# the same answer as running a bunch of separate merges.
      +
      +test_expect_success 'check the input format when --stdin is passed' '
      +	test_when_finished "rm -rf repo" &&