commit: move post-rewrite code to libgit

Move run_rewrite_hook() from bulitin/commit.c to sequencer.c so it can
be shared with other commands and add a new function
commit_post_rewrite() based on the code in builtin/commit.c that
encapsulates rewriting notes and running the post-rewrite hook. Once
the sequencer learns how to create commits without forking 'git
commit' these functions will be used when squashing commits.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -31,9 +31,7 @@
 #include "gpg-interface.h"
 #include "column.h"
 #include "sequencer.h"
-#include "notes-utils.h"
 #include "mailmap.h"
-#include "sigchain.h"
 
 static const char * const builtin_commit_usage[] = {
 	N_("git commit [<options>] [--] <pathspec>..."),
@@ -1478,37 +1476,6 @@ static int git_commit_config(const char *k, const char *v, void *cb)
 	return git_status_config(k, v, s);
 }
 
-static int run_rewrite_hook(const struct object_id *oldoid,
-			    const struct object_id *newoid)
-{
-	struct child_process proc = CHILD_PROCESS_INIT;
-	const char *argv[3];
-	int code;
-	struct strbuf sb = STRBUF_INIT;
-
-	argv[0] = find_hook("post-rewrite");
-	if (!argv[0])
-		return 0;
-
-	argv[1] = "amend";
-	argv[2] = NULL;
-
-	proc.argv = argv;
-	proc.in = -1;
-	proc.stdout_to_stderr = 1;
-
-	code = start_command(&proc);
-	if (code)
-		return code;
-	strbuf_addf(&sb, "%s %s\n", oid_to_hex(oldoid), oid_to_hex(newoid));
-	sigchain_push(SIGPIPE, SIG_IGN);
-	write_in_full(proc.in, sb.buf, sb.len);
-	close(proc.in);
-	strbuf_release(&sb);
-	sigchain_pop(SIGPIPE);
-	return finish_command(&proc);
-}
-
 int run_commit_hook(int editor_is_used, const char *index_file, const char *name, ...)
 {
 	struct argv_array hook_env = ARGV_ARRAY_INIT;
@@ -1739,14 +1706,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	rerere(0);
 	run_commit_hook(use_editor, get_index_file(), "post-commit", NULL);
 	if (amend && !no_post_rewrite) {
-		struct notes_rewrite_cfg *cfg;
-		cfg = init_copy_notes_for_rewrite("amend");
-		if (cfg) {
-			/* we are amending, so current_head is not NULL */
-			copy_note_for_rewrite(cfg, &current_head->object.oid, &oid);
-			finish_copy_notes_for_rewrite(cfg, "Notes added by 'git commit --amend'");
-		}
-		run_rewrite_hook(&current_head->object.oid, &oid);
+		commit_post_rewrite(current_head, &oid);
 	}
 	if (!quiet)
 		print_summary(prefix, &oid, !current_head);

sequencer.c

@@ -21,6 +21,8 @@
 #include "log-tree.h"
 #include "wt-status.h"
 #include "hashmap.h"
+#include "notes-utils.h"
+#include "sigchain.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
@@ -789,6 +791,51 @@ int update_head_with_reflog(const struct commit *old_head,
 	return ret;
 }
 
+static int run_rewrite_hook(const struct object_id *oldoid,
+			    const struct object_id *newoid)
+{
+	struct child_process proc = CHILD_PROCESS_INIT;
+	const char *argv[3];
+	int code;
+	struct strbuf sb = STRBUF_INIT;
+
+	argv[0] = find_hook("post-rewrite");
+	if (!argv[0])
+		return 0;
+
+	argv[1] = "amend";
+	argv[2] = NULL;
+
+	proc.argv = argv;
+	proc.in = -1;
+	proc.stdout_to_stderr = 1;
+
+	code = start_command(&proc);
+	if (code)
+		return code;
+	strbuf_addf(&sb, "%s %s\n", oid_to_hex(oldoid), oid_to_hex(newoid));
+	sigchain_push(SIGPIPE, SIG_IGN);
+	write_in_full(proc.in, sb.buf, sb.len);
+	close(proc.in);
+	strbuf_release(&sb);
+	sigchain_pop(SIGPIPE);
+	return finish_command(&proc);
+}
+
+void commit_post_rewrite(const struct commit *old_head,
+			 const struct object_id *new_head)
+{
+	struct notes_rewrite_cfg *cfg;
+
+	cfg = init_copy_notes_for_rewrite("amend");
+	if (cfg) {
+		/* we are amending, so old_head is not NULL */
+		copy_note_for_rewrite(cfg, &old_head->object.oid, new_head);
+		finish_copy_notes_for_rewrite(cfg, "Notes added by 'git commit --amend'");
+	}
+	run_rewrite_hook(&old_head->object.oid, new_head);
+}
+
 static int is_original_commit_empty(struct commit *commit)
 {
 	const struct object_id *ptree_oid;

sequencer.h

@@ -73,4 +73,6 @@ int update_head_with_reflog(const struct commit *old_head,
 			    const struct object_id *new_head,
 			    const char *action, const struct strbuf *msg,
 			    struct strbuf *err);
+void commit_post_rewrite(const struct commit *current_head,
+			 const struct object_id *new_head);
 #endif