Merge branch 'jc/magic-pathspec'

* jc/magic-pathspec:
  setup.c: Fix some "symbol not declared" sparse warnings
  t3703: Skip tests using directory name ":" on Windows
  revision.c: leave a note for "a lone :" enhancement
  t3703, t4208: add test cases for magic pathspec
  rev/path disambiguation: further restrict "misspelled index entry" diag
  fix overslow :/no-such-string-ever-existed diagnostics
  fix overstrict :<path> diagnosis
  grep: use get_pathspec() correctly
  pathspec: drop "lone : means no pathspec" from get_pathspec()
  Revert "magic pathspec: add ":(icase)path" to match case insensitively"
  magic pathspec: add ":(icase)path" to match case insensitively
  magic pathspec: futureproof shorthand form
  magic pathspec: add tentative ":/path/from/top/level" pathspec support

setup.c

@@ -85,8 +85,17 @@ static void NORETURN die_verify_filename(const char *prefix, const char *arg)
 {
 	unsigned char sha1[20];
 	unsigned mode;
-	/* try a detailed diagnostic ... */
-	get_sha1_with_mode_1(arg, sha1, &mode, 0, prefix);
+
+	/*
+	 * Saying "'(icase)foo' does not exist in the index" when the
+	 * user gave us ":(icase)foo" is just stupid.  A magic pathspec
+	 * begins with a colon and is followed by a non-alnum; do not
+	 * let get_sha1_with_mode_1(only_to_die=1) to even trigger.
+	 */
+	if (!(arg[0] == ':' && !isalnum(arg[1])))
+		/* try a detailed diagnostic ... */
+		get_sha1_with_mode_1(arg, sha1, &mode, 1, prefix);
+
 	/* ... or fall back the most general message. */
 	die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
 	    "Use '--' to separate paths from revisions", arg);
@@ -126,6 +135,105 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "Use '--' to separate filenames from revisions", arg);
 }
 
+/*
+ * Magic pathspec
+ *
+ * NEEDSWORK: These need to be moved to dir.h or even to a new
+ * pathspec.h when we restructure get_pathspec() users to use the
+ * "struct pathspec" interface.
+ *
+ * Possible future magic semantics include stuff like:
+ *
+ *	{ PATHSPEC_NOGLOB, '!', "noglob" },
+ *	{ PATHSPEC_ICASE, '\0', "icase" },
+ *	{ PATHSPEC_RECURSIVE, '*', "recursive" },
+ *	{ PATHSPEC_REGEXP, '\0', "regexp" },
+ *
+ */
+#define PATHSPEC_FROMTOP    (1<<0)
+
+static struct pathspec_magic {
+	unsigned bit;
+	char mnemonic; /* this cannot be ':'! */
+	const char *name;
+} pathspec_magic[] = {
+	{ PATHSPEC_FROMTOP, '/', "top" },
+};
+
+/*
+ * Take an element of a pathspec and check for magic signatures.
+ * Append the result to the prefix.
+ *
+ * For now, we only parse the syntax and throw out anything other than
+ * "top" magic.
+ *
+ * NEEDSWORK: This needs to be rewritten when we start migrating
+ * get_pathspec() users to use the "struct pathspec" interface.  For
+ * example, a pathspec element may be marked as case-insensitive, but
+ * the prefix part must always match literally, and a single stupid
+ * string cannot express such a case.
+ */
+static const char *prefix_pathspec(const char *prefix, int prefixlen, const char *elt)
+{
+	unsigned magic = 0;
+	const char *copyfrom = elt;
+	int i;
+
+	if (elt[0] != ':') {
+		; /* nothing to do */
+	} else if (elt[1] == '(') {
+		/* longhand */
+		const char *nextat;
+		for (copyfrom = elt + 2;
+		     *copyfrom && *copyfrom != ')';
+		     copyfrom = nextat) {
+			size_t len = strcspn(copyfrom, ",)");
+			if (copyfrom[len] == ')')
+				nextat = copyfrom + len;
+			else
+				nextat = copyfrom + len + 1;
+			if (!len)
+				continue;
+			for (i = 0; i < ARRAY_SIZE(pathspec_magic); i++)
+				if (strlen(pathspec_magic[i].name) == len &&
+				    !strncmp(pathspec_magic[i].name, copyfrom, len)) {
+					magic |= pathspec_magic[i].bit;
+					break;
+				}
+			if (ARRAY_SIZE(pathspec_magic) <= i)
+				die("Invalid pathspec magic '%.*s' in '%s'",
+				    (int) len, copyfrom, elt);
+		}
+		if (*copyfrom == ')')
+			copyfrom++;
+	} else {
+		/* shorthand */
+		for (copyfrom = elt + 1;
+		     *copyfrom && *copyfrom != ':';
+		     copyfrom++) {
+			char ch = *copyfrom;
+
+			if (!is_pathspec_magic(ch))
+				break;
+			for (i = 0; i < ARRAY_SIZE(pathspec_magic); i++)
+				if (pathspec_magic[i].mnemonic == ch) {
+					magic |= pathspec_magic[i].bit;
+					break;
+				}
+			if (ARRAY_SIZE(pathspec_magic) <= i)
+				die("Unimplemented pathspec magic '%c' in '%s'",
+				    ch, elt);
+		}
+		if (*copyfrom == ':')
+			copyfrom++;
+	}
+
+	if (magic & PATHSPEC_FROMTOP)
+		return xstrdup(copyfrom);
+	else
+		return prefix_path(prefix, prefixlen, copyfrom);
+}
+
 const char **get_pathspec(const char *prefix, const char **pathspec)
 {
 	const char *entry = *pathspec;
@@ -147,8 +255,7 @@ const char **get_pathspec(const char *prefix, const char **pathspec)
 	dst = pathspec;
 	prefixlen = prefix ? strlen(prefix) : 0;
 	while (*src) {
-		const char *p = prefix_path(prefix, prefixlen, *src);
-		*(dst++) = p;
+		*(dst++) = prefix_pathspec(prefix, prefixlen, *src);
 		src++;
 	}
 	*dst = NULL;