[PATCH v2 6/6] rev-list: support NUL-delimited --missing option

[Justin Tobler <jltobler@gmail.com>]

The `--missing={print,print-info}` option for git-rev-list(1) prints
missing objects found while performing the object walk in the form:

        $ git rev-list --missing=print-info <rev>
        ?<oid> [SP <token>=<value>]... LF

Add support for printing missing objects in a NUL-delimited format when
the `-z` option is enabled.

        $ git rev-list -z --missing=print-info <rev>
        <oid> NUL missing=yes NUL [<token>=<value> NUL]...

In this mode, values containing special characters or spaces are printed
as-is without being escaped or quoted. Instead of prefixing the missing
OID with '?', a separate `missing=yes` token/value pair is appended.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
---
 Documentation/rev-list-options.adoc | 13 ++++++------
 builtin/rev-list.c                  | 29 ++++++++++++++++++++-------
 t/t6022-rev-list-missing.sh         | 31 +++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc
index d400d76cf2..145ded5c78 100644
--- a/Documentation/rev-list-options.adoc
+++ b/Documentation/rev-list-options.adoc
@@ -371,8 +371,8 @@ ifdef::git-rev-list[]
 <OID> NUL [<token>=<value> NUL]...
 -----------------------------------------------------------------------
 +
-Additional object metadata, such as object paths or boundary objects, is
-printed using the `<token>=<value>` form. Token values are printed as-is
+Additional object metadata, such as object paths or boundary/missing objects,
+is printed using the `<token>=<value>` form. Token values are printed as-is
 without any encoding/truncation. An OID entry never contains a '=' character
 and thus is used to signal the start of a new object record. Examples:
 +
@@ -380,12 +380,13 @@ and thus is used to signal the start of a new object record. Examples:
 <OID> NUL
 <OID> NUL path=<path> NUL
 <OID> NUL boundary=yes NUL
+<OID> NUL missing=yes NUL [<token>=<value> NUL]...
 -----------------------------------------------------------------------
 +
-This mode is only compatible with the `--objects` and `--boundary` output
-options. Also, revision and pathspec argument parsing on stdin with the
-`--stdin` option is NUL byte delimited instead of using newlines while in this
-mode.
+This mode is only compatible with the `--objects`, `--boundary`, and
+`--missing` output options. Also, revision and pathspec argument parsing on
+stdin with the `--stdin` option is NUL byte delimited instead of using newlines
+while in this mode.
 endif::git-rev-list[]
 
 History Simplification
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 7c6d4b25b0..d7b4dd48ff 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -136,24 +136,39 @@ static void print_missing_object(struct missing_objects_map_entry *entry,
 {
 	struct strbuf sb = STRBUF_INIT;
 
+	if (line_term)
+		putchar('?');
+
+	printf("%s", oid_to_hex(&entry->entry.oid));
+
+	if (!line_term)
+		printf("%cmissing=yes", info_term);
+
 	if (!print_missing_info) {
-		printf("?%s\n", oid_to_hex(&entry->entry.oid));
+		putchar(line_term);
 		return;
 	}
 
 	if (entry->path && *entry->path) {
 		struct strbuf path = STRBUF_INIT;
 
-		strbuf_addstr(&sb, " path=");
-		quote_path(entry->path, NULL, &path, QUOTE_PATH_QUOTE_SP);
-		strbuf_addbuf(&sb, &path);
+		strbuf_addf(&sb, "%cpath=", info_term);
+
+		if (line_term) {
+			quote_path(entry->path, NULL, &path, QUOTE_PATH_QUOTE_SP);
+			strbuf_addbuf(&sb, &path);
+		} else {
+			strbuf_addstr(&sb, entry->path);
+		}
 
 		strbuf_release(&path);
 	}
 	if (entry->type)
-		strbuf_addf(&sb, " type=%s", type_name(entry->type));
+		strbuf_addf(&sb, "%ctype=%s", info_term, type_name(entry->type));
+
+	fwrite(sb.buf, sizeof(char), sb.len, stdout);
+	putchar(line_term);
 
-	printf("?%s%s\n", oid_to_hex(&entry->entry.oid), sb.buf);
 	strbuf_release(&sb);
 }
 
@@ -784,7 +799,7 @@ int cmd_rev_list(int argc,
 		if (revs.graph || revs.verbose_header || show_disk_usage ||
 		    info.show_timestamp || info.header_prefix || bisect_list ||
 		    use_bitmap_index || revs.edge_hint || revs.left_right ||
-		    revs.cherry_mark || arg_missing_action)
+		    revs.cherry_mark)
 			die(_("-z option used with unsupported option"));
 	}
 
diff --git a/t/t6022-rev-list-missing.sh b/t/t6022-rev-list-missing.sh
index 3e2790d4c8..08e92dd002 100755
--- a/t/t6022-rev-list-missing.sh
+++ b/t/t6022-rev-list-missing.sh
@@ -198,4 +198,35 @@ do
 	'
 done
 
+test_expect_success "-z nul-delimited --missing" '
+	test_when_finished rm -rf repo &&
+
+	git init repo &&
+	(
+		cd repo &&
+		git commit --allow-empty -m first &&
+
+		path="foo bar" &&
+		echo foobar >"$path" &&
+		git add -A &&
+		git commit -m second &&
+
+		oid=$(git rev-parse "HEAD:$path") &&
+		type="$(git cat-file -t $oid)" &&
+
+		obj_path=".git/objects/$(test_oid_to_path $oid)" &&
+
+		git rev-list -z --objects --no-object-names \
+			HEAD ^"$oid" >expect &&
+		printf "%s\0missing=yes\0path=%s\0type=%s\0" "$oid" "$path" \
+			"$type" >>expect &&
+
+		mv "$obj_path" "$obj_path.hidden" &&
+		git rev-list -z --objects --no-object-names \
+			--missing=print-info HEAD >actual &&
+
+		test_cmp expect actual
+	)
+'
+
 test_done
-- 
2.49.0.rc2