fast-import: refactor parsing of spaces

When we see a file change in a commit, we expect one of:

  1. A mark.

  2. An "inline" keyword.

  3. An object sha1.

The handling of spaces is inconsistent between the three
options. Option 1 calls a sub-function which checks for the
space, but doesn't parse past it. Option 2 parses the space,
then deliberately avoids moving the pointer past it. Option
3 detects the space locally but doesn't move past it.

This is confusing, because it looks like option 1 forgets to
check for the space (it's just buried). And option 2 checks
for "inline ", but only moves strlen("inline") characters
forward, which looks like a bug but isn't.

We can make this more clear by just having each branch move
past the space as it is checked (and we can replace the
doubled use of "inline" with a call to skip_prefix).

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

fast-import.c

@@ -2269,7 +2269,7 @@ static uintmax_t parse_mark_ref_space(const char **p)
 	char *end;
 
 	mark = parse_mark_ref(*p, &end);
-	if (*end != ' ')
+	if (*end++ != ' ')
 		die("Missing space after mark: %s", command_buf.buf);
 	*p = end;
 	return mark;
@@ -2304,20 +2304,17 @@ static void file_change_m(const char *p, struct branch *b)
 	if (*p == ':') {
 		oe = find_mark(parse_mark_ref_space(&p));
 		hashcpy(sha1, oe->idx.sha1);
-	} else if (starts_with(p, "inline ")) {
+	} else if (skip_prefix(p, "inline ", &p)) {
 		inline_data = 1;
 		oe = NULL; /* not used with inline_data, but makes gcc happy */
-		p += strlen("inline");  /* advance to space */
 	} else {
 		if (get_sha1_hex(p, sha1))
 			die("Invalid dataref: %s", command_buf.buf);
 		oe = find_object(sha1);
 		p += 40;
-		if (*p != ' ')
+		if (*p++ != ' ')
 			die("Missing space after SHA1: %s", command_buf.buf);
 	}
-	assert(*p == ' ');
-	p++;  /* skip space */
 
 	strbuf_reset(&uq);
 	if (!unquote_c_style(&uq, p, &endp)) {
@@ -2474,20 +2471,17 @@ static void note_change_n(const char *p, struct branch *b, unsigned char *old_fa
 	if (*p == ':') {
 		oe = find_mark(parse_mark_ref_space(&p));
 		hashcpy(sha1, oe->idx.sha1);
-	} else if (starts_with(p, "inline ")) {
+	} else if (skip_prefix(p, "inline ", &p)) {
 		inline_data = 1;
 		oe = NULL; /* not used with inline_data, but makes gcc happy */
-		p += strlen("inline");  /* advance to space */
 	} else {
 		if (get_sha1_hex(p, sha1))
 			die("Invalid dataref: %s", command_buf.buf);
 		oe = find_object(sha1);
 		p += 40;
-		if (*p != ' ')
+		if (*p++ != ' ')
 			die("Missing space after SHA1: %s", command_buf.buf);
 	}
-	assert(*p == ' ');
-	p++;  /* skip space */
 
 	/* <commit-ish> */
 	s = lookup_branch(p);
@@ -3003,6 +2997,8 @@ static struct object_entry *parse_treeish_dataref(const char **p)
 			die("Invalid dataref: %s", command_buf.buf);
 		e = find_object(sha1);
 		*p += 40;
+		if (*(*p)++ != ' ')
+			die("Missing space after tree-ish: %s", command_buf.buf);
 	}
 
 	while (!e || e->type != OBJ_TREE)
@@ -3054,8 +3050,6 @@ static void parse_ls(const char *p, struct branch *b)
 		if (!is_null_sha1(root->versions[1].sha1))
 			root->versions[1].mode = S_IFDIR;
 		load_tree(root);
-		if (*p++ != ' ')
-			die("Missing space after tree-ish: %s", command_buf.buf);
 	}
 	if (*p == '"') {
 		static struct strbuf uq = STRBUF_INIT;