[PATCH v2] sequencer: avoid garbled merge machinery messages due to commit labels

From: Elijah Newren <newren@gmail.com>

sequencer's get_message() exists to provide good labels on conflict
hunks; see commits
  d68565402a ("revert: clarify label on conflict hunks", 2010-03-20)
  bf975d379d ("cherry-pick, revert: add a label for ancestor", 2010-03-20)
  043a4492b3 ("sequencer: factor code out of revert builtin", 2012-01-11).
for background on this function.  These labels are of the form
  <commitID>... <commit summary>
or
  parent of <commitID>... <commit summary>
These labels are then passed as branch names to the merge machinery.
However, these labels, as formatted, often also serve to confuse.  For
example, if we have a rename involved in a content merge, then it
results in text such as the following:

    <<<<<<<< HEAD:foo.c
      int j;
    ========
      int counter;
    >>>>>>>> b01dface... Removed unnecessary stuff:bar.c

Or in various conflict messages, it can make it very difficult to read:

    CONFLICT (rename/delete): foo.c deleted in b01dface... Removed
    unnecessary stuff and renamed in HEAD.  Version HEAD of foo.c left
    in tree.

    CONFLICT (file location): dir1/foo.c added in b01dface... Removed
    unnecessary stuff inside a directory that was renamed in HEAD,
    suggesting it should perhaps be moved to dir2/foo.c.

Make a minor change to remove the ellipses and add parentheses around the commit summary; this makes all three examples much easier to read:

    <<<<<<<< HEAD:foo.c
      int j;
    ========
      int counter;
    >>>>>>>> b01dface (Removed unnecessary stuff):bar.c

    CONFLICT (rename/delete): foo.c deleted in b01dface (Removed
    unnecessary stuff) and renamed in HEAD.  Version HEAD of foo.c left
    in tree.

    CONFLICT (file location): dir1/foo.c added in b01dface (Removed
    unnecessary stuff) inside a directory that was renamed in HEAD,
    suggesting it should perhaps be moved to dir2/foo.c.

Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Junio C Hamano <gitster@pobox.com>
---
    sequencer: avoid garbled merge machinery messages due to commit labels
    
    Changes since v1:
    
     * Added Taylor's Reviewed-by, and Junio's Acked-by (I assume that's a
       fair translation of "Looks good", anyway; feel free to adjust when
       you apply otherwise).

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-828%2Fnewren%2Fsequencer-merge-messages-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-828/newren/sequencer-merge-messages-v2
Pull-Request: https://github.com/git/git/pull/828

Range-diff vs v1:

 1:  da49e2eb58 ! 1:  762eb962cc sequencer: avoid garbled merge machinery messages due to commit labels
     @@ Commit message
              suggesting it should perhaps be moved to dir2/foo.c.
      
          Signed-off-by: Elijah Newren <newren@gmail.com>
     +    Reviewed-by: Taylor Blau <me@ttaylorr.com>
     +    Acked-by: Junio C Hamano <gitster@pobox.com>
      
       ## sequencer.c ##
      @@ sequencer.c: static int get_message(struct commit *commit, struct commit_message *out)

 sequencer.c                     |  2 +-
 t/t3404-rebase-interactive.sh   |  2 +-
 t/t3507-cherry-pick-conflict.sh | 20 ++++++++++----------
 3 files changed, 12 insertions(+), 12 deletions(-)