[PATCH] Convert resolve_ref+xstrdup to new resolve_refdup function

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 2011/12/13 Michael Haggerty <mhagger@alum.mit.edu>:
 >> This uses "one 'const char *' pointer that is used for reading data from
 >> and an extra 'char *' pointer that is used only for freeing" approach,
 >> which has two advantages and one disadvantage:
 >> [...]
 >> When naming a "for-freeing" pointer variable, the kind of data the area of
 >> memory happens to contain is of secondary importance. Being deliberately
 >> vague about what the area of memory may contain is a good thing, because
 >> it actively discourages the program from looking at the area via the
 >> pointer if the variable is named "to_free" or something that does not
 >> specify what it contains.
 >
 > The to_free variable could even be declared void* to make it even less
 > (ab)usable.

 Good thinking. Here's the version with "char *foo_to_free" converted
 to "void *foo_to_free".

 builtin/branch.c        |   12 +++++-------
 builtin/checkout.c      |   15 +++++++--------
 builtin/fmt-merge-msg.c |    7 ++++---
 builtin/for-each-ref.c  |    7 ++-----
 builtin/merge.c         |   12 +++++-------
 builtin/notes.c         |    7 ++++---
 builtin/receive-pack.c  |    7 +++----
 builtin/show-branch.c   |    4 +---
 cache.h                 |    1 +
 reflog-walk.c           |   15 ++++++++-------
 refs.c                  |    6 ++++++
 wt-status.c             |    4 +---
 12 files changed, 47 insertions(+), 50 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index e1e486e..c459f0b 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -104,6 +104,7 @@ static int branch_merged(int kind, const char *name,
 	 */
 	struct commit *reference_rev = NULL;
 	const char *reference_name = NULL;
+	void *reference_name_to_free = NULL;
 	int merged;
 
 	if (kind == REF_LOCAL_BRANCH) {
@@ -114,11 +115,9 @@ static int branch_merged(int kind, const char *name,
 		    branch->merge &&
 		    branch->merge[0] &&
 		    branch->merge[0]->dst &&
-		    (reference_name =
-		     resolve_ref(branch->merge[0]->dst, sha1, 1, NULL)) != NULL) {
-			reference_name = xstrdup(reference_name);
+		    (reference_name = reference_name_to_free =
+		     resolve_refdup(branch->merge[0]->dst, sha1, 1, NULL)) != NULL)
 			reference_rev = lookup_commit_reference(sha1);
-		}
 	}
 	if (!reference_rev)
 		reference_rev = head_rev;
@@ -143,7 +142,7 @@ static int branch_merged(int kind, const char *name,
 				"         '%s', even though it is merged to HEAD."),
 				name, reference_name);
 	}
-	free((char *)reference_name);
+	free(reference_name_to_free);
 	return merged;
 }
 
@@ -731,10 +730,9 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 	track = git_branch_track;
 
-	head = resolve_ref("HEAD", head_sha1, 0, NULL);
+	head = resolve_refdup("HEAD", head_sha1, 0, NULL);
 	if (!head)
 		die(_("Failed to resolve HEAD as a valid ref."));
-	head = xstrdup(head);
 	if (!strcmp(head, "HEAD")) {
 		detached = 1;
 	} else {
diff --git a/builtin/checkout.c b/builtin/checkout.c
index b7c6302..00740bd 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -696,17 +696,14 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 {
 	int ret = 0;
 	struct branch_info old;
+	void *path_to_free;
 	unsigned char rev[20];
 	int flag;
 	memset(&old, 0, sizeof(old));
-	old.path = resolve_ref("HEAD", rev, 0, &flag);
-	if (old.path)
-		old.path = xstrdup(old.path);
+	old.path = path_to_free = resolve_refdup("HEAD", rev, 0, &flag);
 	old.commit = lookup_commit_reference_gently(rev, 1);
-	if (!(flag & REF_ISSYMREF)) {
-		free((char *)old.path);
+	if (!(flag & REF_ISSYMREF))
 		old.path = NULL;
-	}
 
 	if (old.path && !prefixcmp(old.path, "refs/heads/"))
 		old.name = old.path + strlen("refs/heads/");
@@ -720,8 +717,10 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 	}
 
 	ret = merge_working_tree(opts, &old, new);
-	if (ret)
+	if (ret) {
+		free(path_to_free);
 		return ret;
+	}
 
 	if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 		orphaned_commit_warning(old.commit);
@@ -729,7 +728,7 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 	update_refs_for_switch(opts, &old, new);
 
 	ret = post_checkout_hook(old.commit, new->commit, 1);
-	free((char *)old.path);
+	free(path_to_free);
 	return ret || opts->writeout_error;
 }
 
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index bdfa0ea..c81a7fe 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -372,14 +372,15 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 	int i = 0, pos = 0;
 	unsigned char head_sha1[20];
 	const char *current_branch;
+	void *current_branch_to_free;
 
 	/* get current branch */
-	current_branch = resolve_ref("HEAD", head_sha1, 1, NULL);
+	current_branch = current_branch_to_free =
+		resolve_refdup("HEAD", head_sha1, 1, NULL);
 	if (!current_branch)
 		die("No current branch");
 	if (!prefixcmp(current_branch, "refs/heads/"))
 		current_branch += 11;
-	current_branch = xstrdup(current_branch);
 
 	/* get a line */
 	while (pos < in->len) {
@@ -421,7 +422,7 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 	}
 
 	strbuf_complete_line(out);
-	free((char *)current_branch);
+	free(current_branch_to_free);
 	return 0;
 }
 
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index d90e5d2..b01d76a 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -628,11 +628,8 @@ static void populate_value(struct refinfo *ref)
 
 	if (need_symref && (ref->flag & REF_ISSYMREF) && !ref->symref) {
 		unsigned char unused1[20];
-		const char *symref;
-		symref = resolve_ref(ref->refname, unused1, 1, NULL);
-		if (symref)
-			ref->symref = xstrdup(symref);
-		else
+		ref->symref = resolve_refdup(ref->refname, unused1, 1, NULL);
+		if (!ref->symref)
 			ref->symref = "";
 	}
 
diff --git a/builtin/merge.c b/builtin/merge.c
index a1c8534..a3cd5e8 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1096,6 +1096,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	struct commit_list *common = NULL;
 	const char *best_strategy = NULL, *wt_strategy = NULL;
 	struct commit_list **remotes = &remoteheads;
+	void *branch_to_free;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_merge_usage, builtin_merge_options);
@@ -1104,12 +1105,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
 	 * current branch.
 	 */
-	branch = resolve_ref("HEAD", head_sha1, 0, &flag);
-	if (branch) {
-		if (!prefixcmp(branch, "refs/heads/"))
-			branch += 11;
-		branch = xstrdup(branch);
-	}
+	branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
+	if (branch && !prefixcmp(branch, "refs/heads/"))
+		branch += 11;
 	if (!branch || is_null_sha1(head_sha1))
 		head_commit = NULL;
 	else
@@ -1520,6 +1518,6 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		ret = suggest_conflicts(option_renormalize);
 
 done:
-	free((char *)branch);
+	free(branch_to_free);
 	return ret;
 }
diff --git a/builtin/notes.c b/builtin/notes.c
index 10b8bc7..667e20a 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -804,6 +804,7 @@ static int merge_commit(struct notes_merge_options *o)
 	struct notes_tree *t;
 	struct commit *partial;
 	struct pretty_print_context pretty_ctx;
+	void *local_ref_to_free;
 	int ret;
 
 	/*
@@ -826,10 +827,10 @@ static int merge_commit(struct notes_merge_options *o)
 	t = xcalloc(1, sizeof(struct notes_tree));
 	init_notes(t, "NOTES_MERGE_PARTIAL", combine_notes_overwrite, 0);
 
-	o->local_ref = resolve_ref("NOTES_MERGE_REF", sha1, 0, NULL);
+	o->local_ref = local_ref_to_free =
+		resolve_refdup("NOTES_MERGE_REF", sha1, 0, NULL);
 	if (!o->local_ref)
 		die("Failed to resolve NOTES_MERGE_REF");
-	o->local_ref = xstrdup(o->local_ref);
 
 	if (notes_merge_commit(o, t, partial, sha1))
 		die("Failed to finalize notes merge");
@@ -846,7 +847,7 @@ static int merge_commit(struct notes_merge_options *o)
 	free_notes(t);
 	strbuf_release(&msg);
 	ret = merge_abort(o);
-	free((char *)o->local_ref);
+	free(local_ref_to_free);
 	return ret;
 }
 
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index b6d957c..62afac3 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -37,6 +37,7 @@ static int prefer_ofs_delta = 1;
 static int auto_update_server_info;
 static int auto_gc = 1;
 static const char *head_name;
+static void *head_name_to_free;
 static int sent_capabilities;
 
 static enum deny_action parse_deny_action(const char *var, const char *value)
@@ -695,10 +696,8 @@ static void execute_commands(struct command *commands, const char *unpacker_erro
 
 	check_aliased_updates(commands);
 
-	free((char *)head_name);
-	head_name = resolve_ref("HEAD", sha1, 0, NULL);
-	if (head_name)
-		head_name = xstrdup(head_name);
+	free(head_name_to_free);
+	head_name = head_name_to_free = resolve_refdup("HEAD", sha1, 0, NULL);
 
 	for (cmd = commands; cmd; cmd = cmd->next)
 		if (!cmd->skip_update)
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 4b480d7..a1f148e 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -726,10 +726,8 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 
 		if (ac == 0) {
 			static const char *fake_av[2];
-			const char *refname;
 
-			refname = resolve_ref("HEAD", sha1, 1, NULL);
-			fake_av[0] = xstrdup(refname);
+			fake_av[0] = resolve_refdup("HEAD", sha1, 1, NULL);
 			fake_av[1] = NULL;
 			av = fake_av;
 			ac = 1;
diff --git a/cache.h b/cache.h
index 8c98d05..4887a3e 100644
--- a/cache.h
+++ b/cache.h
@@ -866,6 +866,7 @@ extern int read_ref(const char *filename, unsigned char *sha1);
  * errno is sometimes set on errors, but not always.
  */
 extern const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *flag);
+extern char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag);
 
 extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
 extern int dwim_log(const char *str, int len, unsigned char *sha1, char **ref);
diff --git a/reflog-walk.c b/reflog-walk.c
index da71a85..64c677f 100644
--- a/reflog-walk.c
+++ b/reflog-walk.c
@@ -50,11 +50,12 @@ static struct complete_reflogs *read_complete_reflog(const char *ref)
 	for_each_reflog_ent(ref, read_one_reflog, reflogs);
 	if (reflogs->nr == 0) {
 		unsigned char sha1[20];
-		const char *name = resolve_ref(ref, sha1, 1, NULL);
+		const char *name;
+		void *name_to_free;
+		name = name_to_free = resolve_refdup(ref, sha1, 1, NULL);
 		if (name) {
-			name = xstrdup(name);
 			for_each_reflog_ent(name, read_one_reflog, reflogs);
-			free((char *)name);
+			free(name_to_free);
 		}
 	}
 	if (reflogs->nr == 0) {
@@ -171,11 +172,11 @@ int add_reflog_for_walk(struct reflog_walk_info *info,
 	else {
 		if (*branch == '\0') {
 			unsigned char sha1[20];
-			const char *head = resolve_ref("HEAD", sha1, 0, NULL);
-			if (!head)
-				die ("No current branch");
 			free(branch);
-			branch = xstrdup(head);
+			branch = resolve_refdup("HEAD", sha1, 0, NULL);
+			if (!branch)
+				die ("No current branch");
+
 		}
 		reflogs = read_complete_reflog(branch);
 		if (!reflogs || reflogs->nr == 0) {
diff --git a/refs.c b/refs.c
index f5cb297..8ffb32f 100644
--- a/refs.c
+++ b/refs.c
@@ -605,6 +605,12 @@ const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *
 	return ref;
 }
 
+char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag)
+{
+	const char *ret = resolve_ref(ref, sha1, reading, flag);
+	return ret ? xstrdup(ret) : NULL;
+}
+
 /* The argument to filter_refs */
 struct ref_filter {
 	const char *pattern;
diff --git a/wt-status.c b/wt-status.c
index 70fdb76..9ffc535 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -111,7 +111,6 @@ void status_printf_more(struct wt_status *s, const char *color,
 void wt_status_prepare(struct wt_status *s)
 {
 	unsigned char sha1[20];
-	const char *head;
 
 	memset(s, 0, sizeof(*s));
 	memcpy(s->color_palette, default_wt_status_colors,
@@ -119,8 +118,7 @@ void wt_status_prepare(struct wt_status *s)
 	s->show_untracked_files = SHOW_NORMAL_UNTRACKED_FILES;
 	s->use_color = -1;
 	s->relative_paths = 1;
-	head = resolve_ref("HEAD", sha1, 0, NULL);
-	s->branch = head ? xstrdup(head) : NULL;
+	s->branch = resolve_refdup("HEAD", sha1, 0, NULL);
 	s->reference = "HEAD";
 	s->fp = stdout;
 	s->index_file = get_index_file();
-- 
1.7.8.36.g69ee2