parse_pathspec: add special flag for max_depth feature

match_pathspec_depth() and tree_entry_interesting() check max_depth
field in order to support "git grep --max-depth". The feature
activation is tied to "recursive" field, which led to some unwanted
activation, e.g. 5c8eeb8 (diff-index: enable recursive pathspec
matching in unpack_trees - 2012-01-15).

This patch decouples the activation from "recursive" field, puts it in
"magic" field instead. This makes sure that only "git grep" can
activate this feature. And because parse_pathspec knows when the
feature is not used, it does not need to sort pathspec (required for
max_depth to work correctly). A small win for non-grep cases.

Even though a new magic flag is introduced, no magic syntax is. The
magic can be only enabled by parse_pathspec() caller. We might someday
want to support ":(maxdepth:10)src." It all depends on actual use
cases.

max_depth feature cannot be enabled via init_pathspec() anymore. But
that's ok because init_pathspec() is on its way to /dev/null.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/grep.c

@@ -858,7 +858,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	}
 
 	parse_pathspec(&pathspec, 0,
-		       PATHSPEC_PREFER_CWD,
+		       PATHSPEC_PREFER_CWD |
+		       (opt.max_depth != -1 ? PATHSPEC_MAXDEPTH_VALID : 0),
 		       prefix, argv + i);
 	pathspec.max_depth = opt.max_depth;
 	pathspec.recursive = 1;

diff-lib.c

@@ -476,7 +476,6 @@ static int diff_cache(struct rev_info *revs,
 	opts.dst_index = NULL;
 	opts.pathspec = &revs->diffopt.pathspec;
 	opts.pathspec->recursive = 1;
-	opts.pathspec->max_depth = -1;
 
 	init_tree_desc(&t, tree->buffer, tree->size);
 	return unpack_trees(1, &t, &opts);

dir.c

@@ -341,7 +341,9 @@ int match_pathspec_depth(const struct pathspec *ps,
 	int i, retval = 0;
 
 	if (!ps->nr) {
-		if (!ps->recursive || ps->max_depth == -1)
+		if (!ps->recursive ||
+		    !(ps->magic & PATHSPEC_MAXDEPTH) ||
+		    ps->max_depth == -1)
 			return MATCHED_RECURSIVELY;
 
 		if (within_depth(name, namelen, 0, ps->max_depth))
@@ -358,7 +360,9 @@ int match_pathspec_depth(const struct pathspec *ps,
 		if (seen && seen[i] == MATCHED_EXACTLY)
 			continue;
 		how = match_pathspec_item(ps->items+i, prefix, name, namelen);
-		if (ps->recursive && ps->max_depth != -1 &&
+		if (ps->recursive &&
+		    (ps->magic & PATHSPEC_MAXDEPTH) &&
+		    ps->max_depth != -1 &&
 		    how && how != MATCHED_FNMATCH) {
 			int len = ps->items[i].len;
 			if (name[len] == '/')

pathspec.c

@@ -267,6 +267,9 @@ void parse_pathspec(struct pathspec *pathspec,
 
 	memset(pathspec, 0, sizeof(*pathspec));
 
+	if (flags & PATHSPEC_MAXDEPTH_VALID)
+		pathspec->magic |= PATHSPEC_MAXDEPTH;
+
 	/* No arguments, no prefix -> no pathspec */
 	if (!entry && !prefix)
 		return;
@@ -322,6 +325,7 @@ void parse_pathspec(struct pathspec *pathspec,
 		pathspec->magic |= item[i].magic;
 	}
 
+	if (pathspec->magic & PATHSPEC_MAXDEPTH)
 		qsort(pathspec->items, pathspec->nr,
 		      sizeof(struct pathspec_item), pathspec_item_cmp);
 }

pathspec.h

@@ -3,7 +3,10 @@
 
 /* Pathspec magic */
 #define PATHSPEC_FROMTOP	(1<<0)
-#define PATHSPEC_ALL_MAGIC PATHSPEC_FROMTOP
+#define PATHSPEC_MAXDEPTH	(1<<1)
+#define PATHSPEC_ALL_MAGIC	  \
+	(PATHSPEC_FROMTOP	| \
+	 PATHSPEC_MAXDEPTH)
 
 #define PATHSPEC_ONESTAR 1	/* the pathspec pattern sastisfies GFNM_ONESTAR */
 
@@ -27,6 +30,7 @@ struct pathspec {
 /* parse_pathspec flags */
 #define PATHSPEC_PREFER_CWD (1<<0) /* No args means match cwd */
 #define PATHSPEC_PREFER_FULL (1<<1) /* No args means match everything */
+#define PATHSPEC_MAXDEPTH_VALID (1<<2) /* max_depth field is valid */
 
 extern int init_pathspec(struct pathspec *, const char **);
 extern void parse_pathspec(struct pathspec *pathspec,

tree-diff.c

@@ -138,7 +138,6 @@ int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
 
 	/* Enable recursion indefinitely */
 	opt->pathspec.recursive = DIFF_OPT_TST(opt, RECURSIVE);
-	opt->pathspec.max_depth = -1;
 
 	strbuf_init(&base, PATH_MAX);
 	strbuf_add(&base, base_str, baselen);

tree-walk.c

@@ -637,7 +637,9 @@ enum interesting tree_entry_interesting(const struct name_entry *entry,
 		entry_not_interesting : all_entries_not_interesting;
 
 	if (!ps->nr) {
-		if (!ps->recursive || ps->max_depth == -1)
+		if (!ps->recursive ||
+		    !(ps->magic & PATHSPEC_MAXDEPTH) ||
+		    ps->max_depth == -1)
 			return all_entries_interesting;
 		return within_depth(base->buf + base_offset, baselen,
 				    !!S_ISDIR(entry->mode),
@@ -658,7 +660,9 @@ enum interesting tree_entry_interesting(const struct name_entry *entry,
 			if (!match_dir_prefix(base_str, match, matchlen))
 				goto match_wildcards;
 
-			if (!ps->recursive || ps->max_depth == -1)
+			if (!ps->recursive ||
+			    !(ps->magic & PATHSPEC_MAXDEPTH) ||
+			    ps->max_depth == -1)
 				return all_entries_interesting;
 
 			return within_depth(base_str + matchlen + 1,