Re: [PATCH 7/8] merge-tree: support saving merge messages to a separate file

[Elijah Newren <newren@gmail.com>]

On Mon, Jan 3, 2022 at 4:31 AM Fabian Stelzer <fs@gigacodes.de> wrote:
>
> On 31.12.2021 05:04, Elijah Newren via GitGitGadget wrote:
> >From: Elijah Newren <newren@gmail.com>
> >
> >When running `git merge-tree --real`, we previously would only return an
> >exit status reflecting the cleanness of a merge, and print out the
> >toplevel tree of the resulting merge.  Merges also have informational
> >messages, ("Auto-merging <PATH>", "CONFLICT (content): ...", "CONFLICT
> >(file/directory)", etc.)  In fact, when non-content conflicts occur
> >(such as file/directory, modify/delete, add/add with differing modes,
> >rename/rename (1to2), etc.), these informational messages are often the
> >only notification since these conflicts are not representable in the
> >contents of the file.
> >
> >Add a --messages option which names a file so that callers can request
> >these messages be recorded somewhere.
> >
> >Signed-off-by: Elijah Newren <newren@gmail.com>
> >---
> > Documentation/git-merge-tree.txt |  6 ++++--
> > builtin/merge-tree.c             | 18 ++++++++++++++++--
> > t/t4301-merge-tree-real.sh       | 18 ++++++++++++++++++
> > 3 files changed, 38 insertions(+), 4 deletions(-)
> >
> >diff --git a/Documentation/git-merge-tree.txt b/Documentation/git-merge-tree.txt
> >index 5823938937f..4d5857b390b 100644
> >--- a/Documentation/git-merge-tree.txt
> >+++ b/Documentation/git-merge-tree.txt
> >@@ -9,7 +9,7 @@ git-merge-tree - Perform merge without touching index or working tree
> > SYNOPSIS
> > --------
> > [verse]
> >-'git merge-tree' --real <branch1> <branch2>
> >+'git merge-tree' --real [--messages=<file>] <branch1> <branch2>
> > 'git merge-tree' <base-tree> <branch1> <branch2>
> >
> > DESCRIPTION
> >@@ -21,7 +21,9 @@ The first form will merge the two branches, doing a full recursive
> > merge with rename detection.  If the merge is clean, the exit status
> > will be `0`, and if the merge has conflicts, the exit status will be
> > `1`.  The output will consist solely of the resulting toplevel tree
> >-(which may have files including conflict markers).
> >+(which may have files including conflict markers).  With `--messages`,
> >+it will write any informational messages (such as "Auto-merging
> >+<path>" and conflict notices) to the given file.
> >
> > The second form is meant for backward compatibility and will only do a
> > trival merge.  It reads three tree-ish, and outputs trivial merge
> >diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
> >index c5757bed5bb..47deef0b199 100644
> >--- a/builtin/merge-tree.c
> >+++ b/builtin/merge-tree.c
> >@@ -389,6 +389,7 @@ static int trivial_merge(const char *base,
> >
> > struct merge_tree_options {
> >       int real;
> >+      char *messages_file;
> > };
> >
> > static int real_merge(struct merge_tree_options *o,
> >@@ -442,8 +443,15 @@ static int real_merge(struct merge_tree_options *o,
> >        */
> >
> >       merge_incore_recursive(&opt, merge_bases, parent1, parent2, &result);
> >+
> >+      if (o->messages_file) {
> >+              FILE *fp = xfopen(o->messages_file, "w");
> >+              merge_display_update_messages(&opt, &result, fp);
> >+              fclose(fp);
>
> I don't know enough about how merge-ort works internally, but it looks to me
> like at this point the merge already happened and we just didn't clean up
> (finalize) yet. It feels wrong to die() at this point just because we can't
> open messages_file.

Yes, the merge already happened; there now exists a new toplevel tree
(that nothing references).  I'm not sure I understand what's wrong
with die'ing here, though.  I can't tell if you want to defer the
die-ing until later, or just avoid the die-ing and return some kind of
success despite failing to complete what the user requested.

>
> >+      }
> >       printf("%s\n", oid_to_hex(&result.tree->object.oid));
> >-      merge_switch_to_result(&opt, NULL, &result, 0, 0);
> >+
> >+      merge_finalize(&opt, &result);
> >       return result.clean ? 0 : 1;
> > }
> >