[PATCH v1 14/45] Guard against new pathspec magic in pathspec matching code

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

GUARD_PATHSPEC() marks pathspec-sensitive code (basically anything in
'struct pathspec' except fields "nr" and "original"). GUARD_PATHSPEC()
is not supposed to fail. The steps for a new pathspec magic or
optimization would be:

 - update parse_pathspec, add extra information to struct pathspec

 - grep GUARD_PATHSPEC() and update all relevant code (or note those
   that won't work with your new stuff). Update GUARD_PATHSPEC mask
   accordingly.

 - update parse_pathspec calls to disable new magic early at command
   parsing level. Make sure parse_pathspec() catches unsupported
   syntax, not until GUARD_PATHSPEC catches it.

 - add tests to verify supported/unsupported commands both work as
   expected.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/diff.c |  2 ++
 dir.c          |  2 ++
 pathspec.h     |  7 +++++++
 tree-diff.c    | 19 +++++++++++++++++++
 tree-walk.c    |  2 ++
 5 files changed, 32 insertions(+)

diff --git a/builtin/diff.c b/builtin/diff.c
index 8c2af6c..d237e0a 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -371,6 +371,8 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 		die(_("unhandled object '%s' given."), name);
 	}
 	if (rev.prune_data.nr) {
+		/* builtin_diff_b_f() */
+		GUARD_PATHSPEC(&rev.prune_data, PATHSPEC_FROMTOP);
 		if (!path)
 			path = rev.prune_data.items[0].match;
 		paths += rev.prune_data.nr;
diff --git a/dir.c b/dir.c
index 1e9db41..6094ba8 100644
--- a/dir.c
+++ b/dir.c
@@ -297,6 +297,8 @@ int match_pathspec_depth(const struct pathspec *ps,
 {
 	int i, retval = 0;
 
+	GUARD_PATHSPEC(ps, PATHSPEC_FROMTOP | PATHSPEC_MAXDEPTH);
+
 	if (!ps->nr) {
 		if (!ps->recursive ||
 		    !(ps->magic & PATHSPEC_MAXDEPTH) ||
diff --git a/pathspec.h b/pathspec.h
index 1cef9c6..ed5d3a6 100644
--- a/pathspec.h
+++ b/pathspec.h
@@ -27,6 +27,13 @@ struct pathspec {
 	} *items;
 };
 
+#define GUARD_PATHSPEC(ps, mask) \
+	do { \
+		if ((ps)->magic & ~(mask))	       \
+			die("BUG:%s:%d: unsupported magic %x",	\
+			    __FILE__, __LINE__, (ps)->magic & ~(mask)); \
+	} while (0)
+
 /* 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 */
diff --git a/tree-diff.c b/tree-diff.c
index 826512e..5a87614 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -198,6 +198,25 @@ static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, co
 	const char *paths[1];
 	int i;
 
+	/*
+	 * follow-rename code is very specific, we need exactly one
+	 * path. Magic that matches more than one path is not
+	 * supported.
+	 */
+	GUARD_PATHSPEC(&opt->pathspec, PATHSPEC_FROMTOP);
+#if 0
+	/*
+	 * We should reject wildcards as well. Unfortunately we
+	 * haven't got a reliable way to detect that 'foo\*bar' in
+	 * fact has no wildcards. nowildcard_len is merely a hint for
+	 * optimization. Let it slip for now until wildmatch is taught
+	 * about dry-run mode and returns wildcard info.
+	 */
+	if (opt->pathspec.has_wildcard)
+		die("BUG:%s:%d: wildcards are not supported",
+		    __FILE__, __LINE__);
+#endif
+
 	/* Remove the file creation entry from the diff queue, and remember it */
 	choice = q->queue[0];
 	q->nr = 0;
diff --git a/tree-walk.c b/tree-walk.c
index d399ca9..37b157e 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -636,6 +636,8 @@ enum interesting tree_entry_interesting(const struct name_entry *entry,
 	enum interesting never_interesting = ps->has_wildcard ?
 		entry_not_interesting : all_entries_not_interesting;
 
+	GUARD_PATHSPEC(ps, PATHSPEC_FROMTOP | PATHSPEC_MAXDEPTH);
+
 	if (!ps->nr) {
 		if (!ps->recursive ||
 		    !(ps->magic & PATHSPEC_MAXDEPTH) ||
-- 
1.8.0.rc0.19.g7bbb31d