diff --git a/Makefile b/Makefile
index 13293d33fd..48facad01a 100644
--- a/Makefile
+++ b/Makefile
@@ -645,6 +645,7 @@ LIB_H += pack-refs.h
 LIB_H += pack-revindex.h
 LIB_H += parse-options.h
 LIB_H += patch-ids.h
+LIB_H += pathspec.h
 LIB_H += pkt-line.h
 LIB_H += progress.h
 LIB_H += prompt.h
@@ -758,6 +759,7 @@ LIB_OBJS += parse-options-cb.o
 LIB_OBJS += patch-delta.o
 LIB_OBJS += patch-ids.o
 LIB_OBJS += path.o
+LIB_OBJS += pathspec.o
 LIB_OBJS += pkt-line.o
 LIB_OBJS += preload-index.o
 LIB_OBJS += pretty.o
diff --git a/builtin/add.c b/builtin/add.c
index 1f62ba3d2e..e51ba441ca 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -6,6 +6,7 @@
 #include "cache.h"
 #include "builtin.h"
 #include "dir.h"
+#include "pathspec.h"
 #include "exec_cmd.h"
 #include "cache-tree.h"
 #include "run-command.h"
@@ -97,39 +98,6 @@ int add_files_to_cache(const char *prefix, const char **pathspec, int flags)
 	return !!data.add_errors;
 }
 
-static void fill_pathspec_matches(const char **pathspec, char *seen, int specs)
-{
-	int num_unmatched = 0, i;
-
-	/*
-	 * Since we are walking the index as if we were walking the directory,
-	 * we have to mark the matched pathspec as seen; otherwise we will
-	 * mistakenly think that the user gave a pathspec that did not match
-	 * anything.
-	 */
-	for (i = 0; i < specs; i++)
-		if (!seen[i])
-			num_unmatched++;
-	if (!num_unmatched)
-		return;
-	for (i = 0; i < active_nr; i++) {
-		struct cache_entry *ce = active_cache[i];
-		match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, seen);
-	}
-}
-
-static char *find_used_pathspec(const char **pathspec)
-{
-	char *seen;
-	int i;
-
-	for (i = 0; pathspec[i];  i++)
-		; /* just counting */
-	seen = xcalloc(i, 1);
-	fill_pathspec_matches(pathspec, seen, i);
-	return seen;
-}
-
 static char *prune_directory(struct dir_struct *dir, const char **pathspec, int prefix)
 {
 	char *seen;
diff --git a/pathspec.c b/pathspec.c
new file mode 100644
index 0000000000..1472af89ce
--- /dev/null
+++ b/pathspec.c
@@ -0,0 +1,57 @@
+#include "cache.h"
+#include "dir.h"
+#include "pathspec.h"
+
+/*
+ * Finds which of the given pathspecs match items in the index.
+ *
+ * For each pathspec, sets the corresponding entry in the seen[] array
+ * (which should be specs items long, i.e. the same size as pathspec)
+ * to the nature of the "closest" (i.e. most specific) match found for
+ * that pathspec in the index, if it was a closer type of match than
+ * the existing entry.  As an optimization, matching is skipped
+ * altogether if seen[] already only contains non-zero entries.
+ *
+ * If seen[] has not already been written to, it may make sense
+ * to use find_used_pathspec() instead.
+ */
+void fill_pathspec_matches(const char **pathspec, char *seen, int specs)
+{
+	int num_unmatched = 0, i;
+
+	/*
+	 * Since we are walking the index as if we were walking the directory,
+	 * we have to mark the matched pathspec as seen; otherwise we will
+	 * mistakenly think that the user gave a pathspec that did not match
+	 * anything.
+	 */
+	for (i = 0; i < specs; i++)
+		if (!seen[i])
+			num_unmatched++;
+	if (!num_unmatched)
+		return;
+	for (i = 0; i < active_nr; i++) {
+		struct cache_entry *ce = active_cache[i];
+		match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, seen);
+	}
+}
+
+/*
+ * Finds which of the given pathspecs match items in the index.
+ *
+ * This is a one-shot wrapper around fill_pathspec_matches() which
+ * allocates, populates, and returns a seen[] array indicating the
+ * nature of the "closest" (i.e. most specific) matches which each of
+ * the given pathspecs achieves against all items in the index.
+ */
+char *find_used_pathspec(const char **pathspec)
+{
+	char *seen;
+	int i;
+
+	for (i = 0; pathspec[i];  i++)
+		; /* just counting */
+	seen = xcalloc(i, 1);
+	fill_pathspec_matches(pathspec, seen, i);
+	return seen;
+}
diff --git a/pathspec.h b/pathspec.h
new file mode 100644
index 0000000000..1cb1909e4c
--- /dev/null
+++ b/pathspec.h
@@ -0,0 +1,7 @@
+#ifndef PATHSPEC_H
+#define PATHSPEC_H
+
+extern char *find_used_pathspec(const char **pathspec);
+extern void fill_pathspec_matches(const char **pathspec, char *seen, int specs);
+
+#endif /* PATHSPEC_H */