[PATCH v3 09/15] merge-tree: support including merge messages in output

From

Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>

Date

Feb 2, 2022, 07:34 UTC

Message-ID

<c8ed002408d82dc0f1a059a117cd4fd7113d8b07.1643787281.git.gitgitgadget@gmail.com>

In-Reply-To

<pull.1122.v3.git.1643787281.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

When running `git merge-tree --write-tree`, 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, such as:
  * "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 may be the only notification the
user gets since these conflicts are not representable in the contents
of the file.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 Documentation/git-merge-tree.txt | 45 +++++++++++++++++++++++++++-----
 builtin/merge-tree.c             | 19 ++++++++++++--
 t/t4301-merge-tree-write-tree.sh | 21 +++++++++++++++
 3 files changed, 76 insertions(+), 9 deletions(-)

diff --git a/Documentation/git-merge-tree.txt b/Documentation/git-merge-tree.txt
index 569485815a0..42e0f8f6183 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' [--write-tree] <branch1> <branch2>
+'git merge-tree' [--write-tree] [<options>] <branch1> <branch2>
 'git merge-tree' [--trivial-merge] <base-tree> <branch1> <branch2> (deprecated)
 
 DESCRIPTION
@@ -35,17 +35,47 @@ merge is distinguished from a trivial merge in that it includes:
 After the merge completes, it will create a new toplevel tree object.
 See `OUTPUT` below for details.
 
+OPTIONS
+-------
+
+--[no-]messages::
+	Write any informational messages such as "Auto-merging <path>"
+	or CONFLICT notices to the end of stdout.  If unspecified, the
+	default is to include these messages if there are merge
+	conflicts, and to omit them otherwise.
+
 OUTPUT
 ------
 
-For either a successful or conflicted merge, the output from
-git-merge-tree is simply one line:
+By default, for a successful merge, the output from git-merge-tree is
+simply one line:
+
+	<OID of toplevel tree>
+
+Whereas for a conflicted merge, the output is by default of the form:
 
 	<OID of toplevel tree>
+	<Informational messages>
+
+These are discussed individually below.
+
+OID of toplevel tree
+~~~~~~~~~~~~~~~~~~~~
+
+This is a tree object that represents what would be checked out in the
+working tree at the end of `git merge`.  If there were conflicts, then
+files within this tree may have embedded conflict markers.
+
+Informational messages
+~~~~~~~~~~~~~~~~~~~~~~
+
+This always starts with a blank line to separate it from the previous
+section, and then has free-form messages about the merge, such as:
 
-The printed tree object corresponds to what would be checked out in
-the working tree at the end of `git merge`, and thus may have files
-with conflict markers in them.
+  * "Auto-merging <file>"
+  * "CONFLICT (rename/delete): <oldfile> renamed...but deleted in..."
+  * "Failed to merge submodule <submodule> (<reason>)"
+  * "Warning: cannot merge binary files: <filename>"
 
 EXIT STATUS
 -----------
@@ -69,7 +99,8 @@ be used as a part of a series of steps such as
 
 However, it does not quite fit into the same category of low-level
 plumbing commands since the possibility of merge conflicts give it a
-much higher chance of the command not succeeding.
+much higher chance of the command not succeeding (and NEWTREE containing
+a bunch of stuff other than just a toplevel tree).
 
 GIT
 ---
diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index d14c9f6e44e..6a556ab1c9c 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -390,6 +390,7 @@ static int trivial_merge(const char *base,
 
 struct merge_tree_options {
 	int mode;
+	int show_messages;
 };
 
 static int real_merge(struct merge_tree_options *o,
@@ -432,18 +433,27 @@ static int real_merge(struct merge_tree_options *o,
 	merge_incore_recursive(&opt, merge_bases, parent1, parent2, &result);
 	if (result.clean < 0)
 		die(_("failure to merge"));
+
+	if (o->show_messages == -1)
+		o->show_messages = !result.clean;
+
 	puts(oid_to_hex(&result.tree->object.oid));
+	if (o->show_messages) {
+		printf("\n");
+		merge_display_update_messages(&opt, &result, stdout);
+	}
 	merge_finalize(&opt, &result);
 	return !result.clean; /* result.clean < 0 handled above */
 }
 
 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 {
-	struct merge_tree_options o = { 0 };
+	struct merge_tree_options o = { .show_messages = -1 };
 	int expected_remaining_argc;
+	int original_argc;
 
 	const char * const merge_tree_usage[] = {
-		N_("git merge-tree [--write-tree] <branch1> <branch2>"),
+		N_("git merge-tree [--write-tree] [<options>] <branch1> <branch2>"),
 		N_("git merge-tree [--trivial-merge] <base-tree> <branch1> <branch2>"),
 		NULL
 	};
@@ -453,10 +463,13 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 			    'w'),
 		OPT_CMDMODE(0, "trivial-merge", &o.mode,
 			    N_("do a trivial merge only"), 't'),
+		OPT_BOOL(0, "messages", &o.show_messages,
+			 N_("also show informational/conflict messages")),
 		OPT_END()
 	};
 
 	/* Parse arguments */
+	original_argc = argc;
 	argc = parse_options(argc, argv, prefix, mt_options,
 			     merge_tree_usage, PARSE_OPT_STOP_AT_NON_OPTION);
 	if (o.mode) {
@@ -468,6 +481,8 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 			usage_with_options(merge_tree_usage, mt_options);
 		o.mode = (argc == 2 ? 'w' : 't');
 	}
+	if (o.mode == 't' && original_argc < argc)
+		die(_("--trivial-merge is incompatible with all other options"));
 
 	/* Do the relevant type of merge */
 	if (o.mode == 'w')
diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
index 66c3eaf2021..e2255711f9c 100755
--- a/t/t4301-merge-tree-write-tree.sh
+++ b/t/t4301-merge-tree-write-tree.sh
@@ -85,4 +85,25 @@ test_expect_success 'Barf on too many arguments' '
 	grep "^usage: git merge-tree" expect
 '
 
+test_expect_success 'test conflict notices and such' '
+	test_expect_code 1 git merge-tree --write-tree side1 side2 >out &&
+	sed -e "s/[0-9a-f]\{40,\}/HASH/g" out >actual &&
+
+	# 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 &&
+	HASH
+
+	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 actual
+'
+
 test_done

-- 
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