Merge branch 'wp/sha1-name-negative-match'

A new "<branch>^{/!-<pattern>}" notation can be used to name a
commit that is reachable from <branch> that does not match the
given <pattern>.

* wp/sha1-name-negative-match:
  object name: introduce '^{/!-<negative pattern>}' notation
  test for '!' handling in rev-parse's named commits

Documentation/revisions.txt

@@ -176,11 +176,12 @@ existing tag object.
   A colon, followed by a slash, followed by a text, names
   a commit whose commit message matches the specified regular expression.
   This name returns the youngest matching commit which is
-  reachable from any ref.  If the commit message starts with a
-  '!' you have to repeat that;  the special sequence ':/!',
-  followed by something else than '!', is reserved for now.
-  The regular expression can match any part of the commit message. To
-  match messages starting with a string, one can use e.g. ':/^foo'.
+  reachable from any ref. The regular expression can match any part of the
+  commit message. To match messages starting with a string, one can use
+  e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
+  is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
+  literal '!' character, followed by 'foo'. Any other sequence beginning with
+  ':/!' is reserved for now.
 
 '<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
   A suffix ':' followed by a path names the blob or tree

sha1_name.c

@@ -848,8 +848,12 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
  * through history and returning the first commit whose message starts
  * the given regular expression.
  *
- * For future extension, ':/!' is reserved. If you want to match a message
- * beginning with a '!', you have to repeat the exclamation mark.
+ * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
+ *
+ * For a literal '!' character at the beginning of a pattern, you have to repeat
+ * that, like: ':/!!foo'
+ *
+ * For future extension, all other sequences beginning with ':/!' are reserved.
  */
 
 /* Remember to update object flag allocation in object.h */
@@ -878,12 +882,18 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 {
 	struct commit_list *backup = NULL, *l;
 	int found = 0;
+	int negative = 0;
 	regex_t regex;
 
 	if (prefix[0] == '!') {
-		if (prefix[1] != '!')
-			die ("Invalid search pattern: %s", prefix);
 		prefix++;
+
+		if (prefix[0] == '-') {
+			prefix++;
+			negative = 1;
+		} else if (prefix[0] != '!') {
+			die ("Invalid search pattern: %s", prefix);
+		}
 	}
 
 	if (regcomp(&regex, prefix, REG_EXTENDED))
@@ -903,7 +913,7 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 			continue;
 		buf = get_commit_buffer(commit, NULL);
 		p = strstr(buf, "\n\n");
-		matches = p && !regexec(&regex, p + 2, 0, NULL, 0);
+		matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
 		unuse_commit_buffer(commit, buf);
 
 		if (matches) {

t/t1511-rev-parse-caret.sh

@@ -18,7 +18,18 @@ test_expect_success 'setup' '
 	git checkout master &&
 	echo modified >>a-blob &&
 	git add -u &&
-	git commit -m Modified
+	git commit -m Modified &&
+	git branch modref &&
+	echo changed! >>a-blob &&
+	git add -u &&
+	git commit -m !Exp &&
+	git branch expref &&
+	echo changed >>a-blob &&
+	git add -u &&
+	git commit -m Changed &&
+	echo changed-again >>a-blob &&
+	git add -u &&
+	git commit -m Changed-again
 '
 
 test_expect_success 'ref^{non-existent}' '
@@ -77,4 +88,44 @@ test_expect_success 'ref^{/Initial}' '
 	test_cmp expected actual
 '
 
+test_expect_success 'ref^{/!Exp}' '
+	test_must_fail git rev-parse master^{/!Exp}
+'
+
+test_expect_success 'ref^{/!}' '
+	test_must_fail git rev-parse master^{/!}
+'
+
+test_expect_success 'ref^{/!!Exp}' '
+	git rev-parse expref >expected &&
+	git rev-parse master^{/!!Exp} >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref^{/!-}' '
+	test_must_fail git rev-parse master^{/!-}
+'
+
+test_expect_success 'ref^{/!-.}' '
+	test_must_fail git rev-parse master^{/!-.}
+'
+
+test_expect_success 'ref^{/!-non-existent}' '
+	git rev-parse master >expected &&
+	git rev-parse master^{/!-non-existent} >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref^{/!-Changed}' '
+	git rev-parse expref >expected &&
+	git rev-parse master^{/!-Changed} >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'ref^{/!-!Exp}' '
+	git rev-parse modref >expected &&
+	git rev-parse expref^{/!-!Exp} >actual &&
+	test_cmp expected actual
+'
+
 test_done