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

>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);
>+	}

> 	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;
> }
>
>@@ -451,15 +459,18 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
> {
> 	struct merge_tree_options o = { 0 };
> 	int expected_remaining_argc;
>+	int original_argc;
>
> 	const char * const merge_tree_usage[] = {
>-		N_("git merge-tree --real <branch1> <branch2>"),
>+		N_("git merge-tree --real [<options>] <branch1> <branch2>"),
> 		N_("git merge-tree <base-tree> <branch1> <branch2>"),
> 		NULL
> 	};
> 	struct option mt_options[] = {
> 		OPT_BOOL(0, "real", &o.real,
> 			 N_("do a real merge instead of a trivial merge")),
>+		OPT_STRING(0, "messages", &o.messages_file, N_("file"),
>+			   N_("filename to write informational/conflict messages to")),
> 		OPT_END()
> 	};
>
>@@ -468,8 +479,11 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
> 		usage_with_options(merge_tree_usage, mt_options);
>
> 	/* Parse arguments */
>+	original_argc = argc;
> 	argc = parse_options(argc, argv, prefix, mt_options,
> 			     merge_tree_usage, 0);
>+	if (!o.real && original_argc < argc)
>+		die(_("--real must be specified if any other options are"));
> 	expected_remaining_argc = (o.real ? 2 : 3);
> 	if (argc != expected_remaining_argc)
> 		usage_with_options(merge_tree_usage, mt_options);
>diff --git a/t/t4301-merge-tree-real.sh b/t/t4301-merge-tree-real.sh
>index 9fb617ccc7f..42218cdc019 100755
>--- a/t/t4301-merge-tree-real.sh
>+++ b/t/t4301-merge-tree-real.sh
>@@ -78,4 +78,22 @@ test_expect_success 'Barf on too many arguments' '
> 	grep "^usage: git merge-tree" expect
> '
>
>+test_expect_success '--messages gives us the conflict notices and such' '
>+	test_must_fail git merge-tree --real --messages=MSG_FILE side1 side2 &&
>+
>+	# Expected results:
>+	#   "greeting" should merge with conflicts
>+	#   "numbers" should merge cleanly
>+	#   "whatever" has *both* a modify/delete and a file/directory conflict
>+	cat <<-EOF >expect &&
>+	Auto-merging greeting
>+	CONFLICT (content): Merge conflict in greeting
>+	Auto-merging numbers
>+	CONFLICT (file/directory): directory in the way of whatever from side1; moving it to whatever~side1 instead.
>+	CONFLICT (modify/delete): whatever~side1 deleted in side2 and modified in side1.  Version side1 of whatever~side1 left in tree.
>+	EOF
>+
>+	test_cmp expect MSG_FILE
>+'
>+
> test_done
>-- 
>gitgitgadget
>