1 files changed, 34 insertions, 1 deletions

diff --git a/pathspec.h b/pathspec.h
index a27dc81ba2..454ce364fa 100644
--- a/pathspec.h
+++ b/pathspec.h
@@ -22,6 +22,11 @@ struct index_state;
 
 #define PATHSPEC_ONESTAR 1	/* the pathspec pattern satisfies GFNM_ONESTAR */
 
+/**
+ * See glossary-context.txt for the syntax of pathspec.
+ * In memory, a pathspec set is represented by "struct pathspec" and is
+ * prepared by parse_pathspec().
+ */
 struct pathspec {
 	int nr;
 	unsigned int has_wildcard:1;
@@ -73,12 +78,39 @@ struct pathspec {
  */
 #define PATHSPEC_LITERAL_PATH (1<<6)
 
-/*
+/**
  * Given command line arguments and a prefix, convert the input to
  * pathspec. die() if any magic in magic_mask is used.
  *
  * Any arguments used are copied. It is safe for the caller to modify
  * or free 'prefix' and 'args' after calling this function.
+ *
+ * - magic_mask specifies what features that are NOT supported by the following
+ * code. If a user attempts to use such a feature, parse_pathspec() can reject
+ * it early.
+ *
+ * - flags specifies other things that the caller wants parse_pathspec to
+ * perform.
+ *
+ * - prefix and args come from cmd_* functions
+ *
+ * parse_pathspec() helps catch unsupported features and reject them politely.
+ * At a lower level, different pathspec-related functions may not support the
+ * same set of features. Such pathspec-sensitive functions are guarded with
+ * GUARD_PATHSPEC(), which will die in an unfriendly way when an unsupported
+ * feature is requested.
+ *
+ * The command designers are supposed to make sure that GUARD_PATHSPEC() never
+ * dies. They have to make sure all unsupported features are caught by
+ * parse_pathspec(), not by GUARD_PATHSPEC. grepping GUARD_PATHSPEC() should
+ * give the designers all pathspec-sensitive codepaths and what features they
+ * support.
+ *
+ * A similar process is applied when a new pathspec magic is added. The designer
+ * lifts the GUARD_PATHSPEC restriction in the functions that support the new
+ * magic. At the same time (s)he has to make sure this new feature will be
+ * caught at parse_pathspec() in commands that cannot handle the new magic in
+ * some cases. grepping parse_pathspec() should help.
  */
 void parse_pathspec(struct pathspec *pathspec,
 		    unsigned magic_mask,
@@ -95,6 +127,7 @@ void parse_pathspec_file(struct pathspec *pathspec,
 			 const char *prefix,
 			 const char *file,
 			 int nul_term_line);
+
 void copy_pathspec(struct pathspec *dst, const struct pathspec *src);
 void clear_pathspec(struct pathspec *);