[RFC,v1,00/17] Rewrite the remaining merge strategies from shell to C

Message

Alban Gruin June 25, 2020, 12:19 p.m. UTC

In an effort to reduce the number of shell scripts part of git, I
propose this patch converting the two remaining merge strategies,
resolve and octopus, from shell to C.  This will enable slightly better
performance, better integration with git itself (no more forking to
perform these operations), better portability (Windows and shell scripts
don't mix well).

Three scripts are actually converted: first git-merge-one-file.sh, then
git-merge-resolve.sh, and finally git-merge-octopus.sh.  Not only they
are converted, but they also are modified to operate without forking,
and then libified so they can be used by git without spawning another
process.

The first patch is not important to make the whole series work, but I
made this patch while working on this series.

Patches 2-5 rewrite, clean, and libify `git merge-one-file', used by the
resolve and octopus strategies.

Patch 6 libifies `git merge-index', so the rewritten `git
merge-one-file' can be called without forking.

Patch 7-8-9 rewrite, clean, and libify `git merge-resolve'.

Patch 10 moves a function, better_branch_name(), that will prove itself
useful in the C version of `git merge-octopus', but that is not part of
libgit.a.

Patches 11-12-13 rewrite, clean, and libify `git merge-octopus'.

Patches 14-15-16-17 teach `git merge' and the sequencer to call the
strategies without forking.

This series keeps the commands `git merge-one-file', `git merge-resolve'
and `git merge-octopus', so any script depending on them should keep
working without any changes.

This series is based on c9c318d6bf (The fourth batch, 2020-06-22).  The
tip is tagged as "rewrite-and-cleanup-merge-strategies-v1" at
https://github.com/agrn/git.

Alban Gruin (17):
  t6027: modernise tests
  merge-one-file: rewrite in C
  merge-one-file: remove calls to external processes
  merge-one-file: use error() instead of fprintf(stderr, ...)
  merge-one-file: libify merge_one_file()
  merge-index: libify merge_one_path() and merge_all()
  merge-resolve: rewrite in C
  merge-resolve: remove calls to external processes
  merge-resolve: libify merge_resolve()
  merge-recursive: move better_branch_name() to merge.c
  merge-octopus: rewrite in C
  merge-octopus: remove calls to external processes
  merge-octopus: libify merge_octopus()
  merge: use the "resolve" strategy without forking
  merge: use the "octopus" strategy without forking
  sequencer: use the "resolve" strategy without forking
  sequencer: use the "octopus" merge strategy without forking

 Makefile                        |   7 +-
 builtin.h                       |   3 +
 builtin/merge-index.c           |  77 +----
 builtin/merge-octopus.c         |  65 ++++
 builtin/merge-one-file.c        |  74 ++++
 builtin/merge-recursive.c       |  16 +-
 builtin/merge-resolve.c         |  69 ++++
 builtin/merge.c                 |   9 +-
 cache.h                         |   2 +-
 git-merge-octopus.sh            | 112 -------
 git-merge-one-file.sh           | 167 ---------
 git-merge-resolve.sh            |  54 ---
 git.c                           |   3 +
 merge-strategies.c              | 577 ++++++++++++++++++++++++++++++++
 merge-strategies.h              |  44 +++
 merge.c                         |  12 +
 sequencer.c                     |  16 +-
 t/t6027-merge-binary.sh         |  27 +-
 t/t6035-merge-dir-to-symlink.sh |   2 +-
 19 files changed, 889 insertions(+), 447 deletions(-)
 create mode 100644 builtin/merge-octopus.c
 create mode 100644 builtin/merge-one-file.c
 create mode 100644 builtin/merge-resolve.c
 delete mode 100755 git-merge-octopus.sh
 delete mode 100755 git-merge-one-file.sh
 delete mode 100755 git-merge-resolve.sh
 create mode 100644 merge-strategies.c
 create mode 100644 merge-strategies.h