commit: reduce use of redundant global variables

The file-scope global variable head_sha1[] was used to hold the object
name of the current HEAD commit (unless we are about to make an initial
commit). Also there is an independent "static int initial_commit".

Fix all the functions on the call-chain that use these two variables to
take a new "(const) struct commit *current_head" argument instead, and
replace their uses, e.g. "if (initial_commit)" becomes "if (!current_head)"
and a reference to "head_sha1" becomes "current_head->object.sha1".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -62,8 +62,6 @@ N_("The previous cherry-pick is now empty, possibly due to conflict resolution.\
 "\n"
 "Otherwise, please use 'git reset'\n");
 
-static unsigned char head_sha1[20];
-
 static const char *use_message_buffer;
 static const char commit_editmsg[] = "COMMIT_EDITMSG";
 static struct lock_file index_lock; /* real index */
@@ -102,7 +100,7 @@ static enum {
 static char *cleanup_arg;
 
 static enum commit_whence whence;
-static int use_editor = 1, initial_commit, include_status = 1;
+static int use_editor = 1, include_status = 1;
 static int show_ignored_in_status;
 static const char *only_include_assumed;
 static struct strbuf message;
@@ -294,13 +292,13 @@ static void add_remove_files(struct string_list *list)
 	}
 }
 
-static void create_base_index(void)
+static void create_base_index(const struct commit *current_head)
 {
 	struct tree *tree;
 	struct unpack_trees_options opts;
 	struct tree_desc t;
 
-	if (initial_commit) {
+	if (!current_head) {
 		discard_cache();
 		return;
 	}
@@ -313,7 +311,7 @@ static void create_base_index(void)
 	opts.dst_index = &the_index;
 
 	opts.fn = oneway_merge;
-	tree = parse_tree_indirect(head_sha1);
+	tree = parse_tree_indirect(current_head->object.sha1);
 	if (!tree)
 		die(_("failed to unpack HEAD tree object"));
 	parse_tree(tree);
@@ -332,7 +330,8 @@ static void refresh_cache_or_die(int refresh_flags)
 		die_resolve_conflict("commit");
 }
 
-static char *prepare_index(int argc, const char **argv, const char *prefix, int is_status)
+static char *prepare_index(int argc, const char **argv, const char *prefix,
+			   const struct commit *current_head, int is_status)
 {
 	int fd;
 	struct string_list partial;
@@ -448,7 +447,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, int
 
 	memset(&partial, 0, sizeof(partial));
 	partial.strdup_strings = 1;
-	if (list_paths(&partial, initial_commit ? NULL : "HEAD", prefix, pathspec))
+	if (list_paths(&partial, !current_head ? NULL : "HEAD", prefix, pathspec))
 		exit(1);
 
 	discard_cache();
@@ -467,7 +466,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, int
 						(uintmax_t) getpid()),
 				       LOCK_DIE_ON_ERROR);
 
-	create_base_index();
+	create_base_index(current_head);
 	add_remove_files(&partial);
 	refresh_cache(REFRESH_QUIET);
 
@@ -516,12 +515,9 @@ static int run_status(FILE *fp, const char *index_file, const char *prefix, int
 	return s->commitable;
 }
 
-static int is_a_merge(const unsigned char *sha1)
+static int is_a_merge(const struct commit *current_head)
 {
-	struct commit *commit = lookup_commit(sha1);
+	return !!(current_head->parents && current_head->parents->next);
-	if (!commit || parse_commit(commit))
-		die(_("could not parse HEAD commit"));
-	return !!(commit->parents && commit->parents->next);
 }
 
 static const char sign_off_header[] = "Signed-off-by: ";
@@ -625,6 +621,7 @@ static char *cut_ident_timestamp_part(char *string)
 }
 
 static int prepare_to_commit(const char *index_file, const char *prefix,
+			     struct commit *current_head,
 			     struct wt_status *s,
 			     struct strbuf *author_ident)
 {
@@ -846,7 +843,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	 * empty due to conflict resolution, which the user should okay.
 	 */
 	if (!commitable && whence != FROM_MERGE && !allow_empty &&
-	    !(amend && is_a_merge(head_sha1))) {
+	    !(amend && is_a_merge(current_head))) {
 		run_status(stdout, index_file, prefix, 0, s);
 		if (amend)
 			fputs(_(empty_amend_advice), stderr);
@@ -1004,6 +1001,7 @@ static const char *read_commit_message(const char *name)
 static int parse_and_validate_options(int argc, const char *argv[],
 				      const char * const usage[],
 				      const char *prefix,
+				      struct commit *current_head,
 				      struct wt_status *s)
 {
 	int f = 0;
@@ -1024,11 +1022,8 @@ static int parse_and_validate_options(int argc, const char *argv[],
 	if (!use_editor)
 		setenv("GIT_EDITOR", ":", 1);
 
-	if (get_sha1("HEAD", head_sha1))
-		initial_commit = 1;
-
 	/* Sanity check options */
-	if (amend && initial_commit)
+	if (amend && !current_head)
 		die(_("You have nothing to amend."));
 	if (amend && whence != FROM_COMMIT)
 		die(_("You are in the middle of a %s -- cannot amend."), whence_s());
@@ -1100,12 +1095,12 @@ static int parse_and_validate_options(int argc, const char *argv[],
 }
 
 static int dry_run_commit(int argc, const char **argv, const char *prefix,
-			  struct wt_status *s)
+			  const struct commit *current_head, struct wt_status *s)
 {
 	int commitable;
 	const char *index_file;
 
-	index_file = prepare_index(argc, argv, prefix, 1);
+	index_file = prepare_index(argc, argv, prefix, current_head, 1);
 	commitable = run_status(stdout, index_file, prefix, 0, s);
 	rollback_index_files();
 
@@ -1258,7 +1253,8 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
-static void print_summary(const char *prefix, const unsigned char *sha1)
+static void print_summary(const char *prefix, const unsigned char *sha1,
+			  int initial_commit)
 {
 	struct rev_info rev;
 	struct commit *commit;
@@ -1380,12 +1376,13 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	struct strbuf author_ident = STRBUF_INIT;
 	const char *index_file, *reflog_msg;
 	char *nl, *p;
-	unsigned char commit_sha1[20];
+	unsigned char sha1[20];
 	struct ref_lock *ref_lock;
 	struct commit_list *parents = NULL, **pptr = &parents;
 	struct stat statbuf;
 	int allow_fast_forward = 1;
 	struct wt_status s;
+	struct commit *current_head = NULL;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_commit_usage, builtin_commit_options);
@@ -1396,38 +1393,41 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 
 	if (s.use_color == -1)
 		s.use_color = git_use_color_default;
+	if (get_sha1("HEAD", sha1))
+		current_head = NULL;
+	else {
+		current_head = lookup_commit(sha1);
+		if (!current_head || parse_commit(current_head))
+			die(_("could not parse HEAD commit"));
+	}
 	argc = parse_and_validate_options(argc, argv, builtin_commit_usage,
-					  prefix, &s);
+					  prefix, current_head, &s);
 	if (dry_run) {
 		if (diff_use_color_default == -1)
 			diff_use_color_default = git_use_color_default;
-		return dry_run_commit(argc, argv, prefix, &s);
+		return dry_run_commit(argc, argv, prefix, current_head, &s);
 	}
-	index_file = prepare_index(argc, argv, prefix, 0);
+	index_file = prepare_index(argc, argv, prefix, current_head, 0);
 
 	/* Set up everything for writing the commit object.  This includes
 	   running hooks, writing the trees, and interacting with the user.  */
-	if (!prepare_to_commit(index_file, prefix, &s, &author_ident)) {
+	if (!prepare_to_commit(index_file, prefix,
+			       current_head, &s, &author_ident)) {
 		rollback_index_files();
 		return 1;
 	}
 
 	/* Determine parents */
 	reflog_msg = getenv("GIT_REFLOG_ACTION");
-	if (initial_commit) {
+	if (!current_head) {
 		if (!reflog_msg)
 			reflog_msg = "commit (initial)";
 	} else if (amend) {
 		struct commit_list *c;
-		struct commit *commit;
 
 		if (!reflog_msg)
 			reflog_msg = "commit (amend)";
-		commit = lookup_commit(head_sha1);
+		for (c = current_head->parents; c; c = c->next)
-		if (!commit || parse_commit(commit))
-			die(_("could not parse HEAD commit"));
-
-		for (c = commit->parents; c; c = c->next)
 			pptr = &commit_list_insert(c->item, pptr)->next;
 	} else if (whence == FROM_MERGE) {
 		struct strbuf m = STRBUF_INIT;
@@ -1435,7 +1435,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 
 		if (!reflog_msg)
 			reflog_msg = "commit (merge)";
-		pptr = &commit_list_insert(lookup_commit(head_sha1), pptr)->next;
+		pptr = &commit_list_insert(current_head, pptr)->next;
 		fp = fopen(git_path("MERGE_HEAD"), "r");
 		if (fp == NULL)
 			die_errno(_("could not open '%s' for reading"),
@@ -1461,7 +1461,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			reflog_msg = (whence == FROM_CHERRY_PICK)
 					? "commit (cherry-pick)"
 					: "commit";
-		pptr = &commit_list_insert(lookup_commit(head_sha1), pptr)->next;
+		pptr = &commit_list_insert(current_head, pptr)->next;
 	}
 
 	/* Finally, get the commit message */
@@ -1487,7 +1487,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		exit(1);
 	}
 
-	if (commit_tree(sb.buf, active_cache_tree->sha1, parents, commit_sha1,
+	if (commit_tree(sb.buf, active_cache_tree->sha1, parents, sha1,
 			author_ident.buf)) {
 		rollback_index_files();
 		die(_("failed to write commit object"));
@@ -1495,7 +1495,9 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	strbuf_release(&author_ident);
 
 	ref_lock = lock_any_ref_for_update("HEAD",
-					   initial_commit ? NULL : head_sha1,
+					   !current_head
+					   ? NULL
+					   : current_head->object.sha1,
 					   0);
 
 	nl = strchr(sb.buf, '\n');
@@ -1510,7 +1512,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		rollback_index_files();
 		die(_("cannot lock HEAD ref"));
 	}
-	if (write_ref_sha1(ref_lock, commit_sha1, sb.buf) < 0) {
+	if (write_ref_sha1(ref_lock, sha1, sb.buf) < 0) {
 		rollback_index_files();
 		die(_("cannot update HEAD ref"));
 	}
@@ -1532,13 +1534,14 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		struct notes_rewrite_cfg *cfg;
 		cfg = init_copy_notes_for_rewrite("amend");
 		if (cfg) {
-			copy_note_for_rewrite(cfg, head_sha1, commit_sha1);
+			/* we are amending, so current_head is not NULL */
+			copy_note_for_rewrite(cfg, current_head->object.sha1, sha1);
 			finish_copy_notes_for_rewrite(cfg);
 		}
-		run_rewrite_hook(head_sha1, commit_sha1);
+		run_rewrite_hook(current_head->object.sha1, sha1);
 	}
 	if (!quiet)
-		print_summary(prefix, commit_sha1);
+		print_summary(prefix, sha1, !current_head);
 
 	return 0;
 }