use strbuf_complete to conditionally append slash

When working with paths in strbufs, we frequently want to
ensure that a directory contains a trailing slash before
appending to it. We can shorten this code (and make the
intent more obvious) by calling strbuf_complete.

Most of these cases are trivially identical conversions, but
there are two things to note:

  - in a few cases we did not check that the strbuf is
    non-empty (which would lead to an out-of-bounds memory
    access). These were generally not triggerable in
    practice, either from earlier assertions, or typically
    because we would have just fed the strbuf to opendir(),
    which would choke on an empty path.

  - in a few cases we indexed the buffer with "original_len"
    or similar, rather than the current sb->len, and it is
    not immediately obvious from the diff that they are the
    same. In all of these cases, I manually verified that
    the strbuf does not change between the assignment and
    the strbuf_complete call.

This does not convert cases which look like:

  if (sb->len && !is_dir_sep(sb->buf[sb->len - 1]))
	  strbuf_addch(sb, '/');

as those are obviously semantically different. Some of these
cases arguably should be doing that, but that is out of
scope for this change, which aims purely for cleanup with no
behavior change (and at least it will make such sites easier
to find and examine in the future, as we can grep for
strbuf_complete).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clean.c

@@ -159,8 +159,7 @@ static int is_git_repository(struct strbuf *path)
 	int gitfile_error;
 	size_t orig_path_len = path->len;
 	assert(orig_path_len != 0);
-	if (path->buf[orig_path_len - 1] != '/')
-		strbuf_addch(path, '/');
+	strbuf_complete(path, '/');
 	strbuf_addstr(path, ".git");
 	if (read_gitfile_gently(path->buf, &gitfile_error) || is_git_directory(path->buf))
 		ret = 1;
@@ -206,8 +205,7 @@ static int remove_dirs(struct strbuf *path, const char *prefix, int force_flag,
 		return res;
 	}
 
-	if (path->buf[original_len - 1] != '/')
-		strbuf_addch(path, '/');
+	strbuf_complete(path, '/');
 
 	len = path->len;
 	while ((e = readdir(dir)) != NULL) {

builtin/log.c

@@ -796,8 +796,7 @@ static int reopen_stdout(struct commit *commit, const char *subject,
 		if (filename.len >=
 		    PATH_MAX - FORMAT_PATCH_NAME_MAX - suffix_len)
 			return error(_("name of output directory is too long"));
-		if (filename.buf[filename.len - 1] != '/')
-			strbuf_addch(&filename, '/');
+		strbuf_complete(&filename, '/');
 	}
 
 	if (rev->numbered_files)

diff-no-index.c

@@ -136,15 +136,13 @@ static int queue_diff(struct diff_options *o,
 
 		if (name1) {
 			strbuf_addstr(&buffer1, name1);
-			if (buffer1.len && buffer1.buf[buffer1.len - 1] != '/')
-				strbuf_addch(&buffer1, '/');
+			strbuf_complete(&buffer1, '/');
 			len1 = buffer1.len;
 		}
 
 		if (name2) {
 			strbuf_addstr(&buffer2, name2);
-			if (buffer2.len && buffer2.buf[buffer2.len - 1] != '/')
-				strbuf_addch(&buffer2, '/');
+			strbuf_complete(&buffer2, '/');
 			len2 = buffer2.len;
 		}
 

dir.c

@@ -1519,8 +1519,7 @@ static enum path_treatment treat_path_fast(struct dir_struct *dir,
 	}
 	strbuf_addstr(path, cdir->ucd->name);
 	/* treat_one_path() does this before it calls treat_directory() */
-	if (path->buf[path->len - 1] != '/')
-		strbuf_addch(path, '/');
+	strbuf_complete(path, '/');
 	if (cdir->ucd->check_only)
 		/*
 		 * check_only is set as a result of treat_directory() getting
@@ -2126,8 +2125,7 @@ static int remove_dir_recurse(struct strbuf *path, int flag, int *kept_up)
 		else
 			return -1;
 	}
-	if (path->buf[original_len - 1] != '/')
-		strbuf_addch(path, '/');
+	strbuf_complete(path, '/');
 
 	len = path->len;
 	while ((e = readdir(dir)) != NULL) {

path.c

@@ -240,8 +240,7 @@ static void do_submodule_path(struct strbuf *buf, const char *path,
 	const char *git_dir;
 
 	strbuf_addstr(buf, path);
-	if (buf->len && buf->buf[buf->len - 1] != '/')
-		strbuf_addch(buf, '/');
+	strbuf_complete(buf, '/');
 	strbuf_addstr(buf, ".git");
 
 	git_dir = read_gitfile(buf->buf);

refs.c

@@ -2193,8 +2193,7 @@ int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
 
 	if (!has_glob_specials(pattern)) {
 		/* Append implied '/' '*' if not present. */
-		if (real_pattern.buf[real_pattern.len - 1] != '/')
-			strbuf_addch(&real_pattern, '/');
+		strbuf_complete(&real_pattern, '/');
 		/* No need to check for '*', there is none. */
 		strbuf_addch(&real_pattern, '*');
 	}

url.c

@@ -120,8 +120,7 @@ char *url_decode_parameter_value(const char **query)
 void end_url_with_slash(struct strbuf *buf, const char *url)
 {
 	strbuf_addstr(buf, url);
-	if (buf->len && buf->buf[buf->len - 1] != '/')
-		strbuf_addch(buf, '/');
+	strbuf_complete(buf, '/');
 }
 
 void str_end_url_with_slash(const char *url, char **dest) {