dir.c: improve docs for match_pathspec() and match_pathspec_depth()

Fix a grammatical issue in the description of these functions, and
make it more obvious how and why seen[] can be reused across multiple
invocations.

Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -167,12 +167,19 @@ static int match_one(const char *match, const char *name, int namelen)
 }
 
 /*
- * Given a name and a list of pathspecs, see if the name matches
- * any of the pathspecs.  The caller is also interested in seeing
- * all pathspec matches some names it calls this function with
- * (otherwise the user could have mistyped the unmatched pathspec),
- * and a mark is left in seen[] array for pathspec element that
- * actually matched anything.
+ * Given a name and a list of pathspecs, returns the nature of the
+ * closest (i.e. most specific) match of the name to any of the
+ * pathspecs.
+ *
+ * The caller typically calls this multiple times with the same
+ * pathspec and seen[] array but with different name/namelen
+ * (e.g. entries from the index) and is interested in seeing if and
+ * how each pathspec matches all the names it calls this function
+ * with.  A mark is left in the seen[] array for each pathspec element
+ * indicating the closest type of match that element achieved, so if
+ * seen[n] remains zero after multiple invocations, that means the nth
+ * pathspec did not match any names, which could indicate that the
+ * user mistyped the nth pathspec.
  */
 int match_pathspec(const char **pathspec, const char *name, int namelen,
 		int prefix, char *seen)
@@ -239,12 +246,19 @@ static int match_pathspec_item(const struct pathspec_item *item, int prefix,
 }
 
 /*
- * Given a name and a list of pathspecs, see if the name matches
- * any of the pathspecs.  The caller is also interested in seeing
- * all pathspec matches some names it calls this function with
- * (otherwise the user could have mistyped the unmatched pathspec),
- * and a mark is left in seen[] array for pathspec element that
- * actually matched anything.
+ * Given a name and a list of pathspecs, returns the nature of the
+ * closest (i.e. most specific) match of the name to any of the
+ * pathspecs.
+ *
+ * The caller typically calls this multiple times with the same
+ * pathspec and seen[] array but with different name/namelen
+ * (e.g. entries from the index) and is interested in seeing if and
+ * how each pathspec matches all the names it calls this function
+ * with.  A mark is left in the seen[] array for each pathspec element
+ * indicating the closest type of match that element achieved, so if
+ * seen[n] remains zero after multiple invocations, that means the nth
+ * pathspec did not match any names, which could indicate that the
+ * user mistyped the nth pathspec.
  */
 int match_pathspec_depth(const struct pathspec *ps,
 			 const char *name, int namelen,

dir.h

@@ -116,6 +116,12 @@ struct dir_struct {
 	char basebuf[PATH_MAX];
 };
 
+/*
+ * The ordering of these constants is significant, with
+ * higher-numbered match types signifying "closer" (i.e. more
+ * specific) matches which will override lower-numbered match types
+ * when populating the seen[] array.
+ */
 #define MATCHED_RECURSIVELY 1
 #define MATCHED_FNMATCH 2
 #define MATCHED_EXACTLY 3