verify_filename(): ask the caller to chose the kind of diagnosis

verify_filename() can be called in two different contexts. Either we
just tried to interpret a string as an object name, and it fails, so
we try looking for a working tree file (i.e. we finished looking at
revs that come earlier on the command line, and the next argument
must be a pathname), or we _know_ that we are looking for a
pathname, and shouldn't even try interpreting the string as an
object name.

For example, with this change, we get:

  $ git log COPYING HEAD:inexistant
  fatal: HEAD:inexistant: no such path in the working tree.
  Use '-- <path>...' to specify paths that do not exist locally.
  $ git log HEAD:inexistant
  fatal: Path 'inexistant' does not exist in 'HEAD'

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/grep.c

@@ -1045,7 +1045,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	if (!seen_dashdash) {
 		int j;
 		for (j = i; j < argc; j++)
-			verify_filename(prefix, argv[j]);
+			verify_filename(prefix, argv[j], j == i);
 	}
 
 	paths = get_pathspec(prefix, argv + i);

builtin/reset.c

@@ -285,7 +285,7 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 			rev = argv[i++];
 		} else {
 			/* Otherwise we treat this as a filename */
-			verify_filename(prefix, argv[i]);
+			verify_filename(prefix, argv[i], 1);
 		}
 	}
 

builtin/rev-parse.c

@@ -486,7 +486,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 
 		if (as_is) {
 			if (show_file(arg) && as_is < 2)
-				verify_filename(prefix, arg);
+				verify_filename(prefix, arg, 0);
 			continue;
 		}
 		if (!strcmp(arg,"-n")) {
@@ -732,7 +732,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		as_is = 1;
 		if (!show_file(arg))
 			continue;
-		verify_filename(prefix, arg);
+		verify_filename(prefix, arg, 1);
 	}
 	if (verify) {
 		if (revs_count == 1) {

cache.h

@@ -452,7 +452,9 @@ extern const char *setup_git_directory(void);
 extern char *prefix_path(const char *prefix, int len, const char *path);
 extern const char *prefix_filename(const char *prefix, int len, const char *path);
 extern int check_filename(const char *prefix, const char *name);
-extern void verify_filename(const char *prefix, const char *name);
+extern void verify_filename(const char *prefix,
+			    const char *name,
+			    int diagnose_misspelt_rev);
 extern void verify_non_filename(const char *prefix, const char *name);
 
 #define INIT_DB_QUIET 0x0001

revision.c

@@ -1755,7 +1755,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 			 * but the latter we have checked in the main loop.
 			 */
 			for (j = i; j < argc; j++)
-				verify_filename(revs->prefix, argv[j]);
+				verify_filename(revs->prefix, argv[j], j == i);
 
 			append_prune_data(&prune_data, argv + i);
 			break;

setup.c

@@ -53,11 +53,17 @@ int check_filename(const char *prefix, const char *arg)
 	die_errno("failed to stat '%s'", arg);
 }
 
-static void NORETURN die_verify_filename(const char *prefix, const char *arg)
+static void NORETURN die_verify_filename(const char *prefix,
+					 const char *arg,
+					 int diagnose_misspelt_rev)
 {
 	unsigned char sha1[20];
 	unsigned mode;
 
+	if (!diagnose_misspelt_rev)
+		die("%s: no such path in the working tree.\n"
+		    "Use '-- <path>...' to specify paths that do not exist locally.",
+		    arg);
 	/*
 	 * Saying "'(icase)foo' does not exist in the index" when the
 	 * user gave us ":(icase)foo" is just stupid.  A magic pathspec
@@ -80,14 +86,29 @@ static void NORETURN die_verify_filename(const char *prefix, const char *arg)
  * as true, because even if such a filename were to exist, we want
  * it to be preceded by the "--" marker (or we want the user to
  * use a format like "./-filename")
+ *
+ * The "diagnose_misspelt_rev" is used to provide a user-friendly
+ * diagnosis when dying upon finding that "name" is not a pathname.
+ * If set to 1, the diagnosis will try to diagnose "name" as an
+ * invalid object name (e.g. HEAD:foo). If set to 0, the diagnosis
+ * will only complain about an inexisting file.
+ *
+ * This function is typically called to check that a "file or rev"
+ * argument is unambiguous. In this case, the caller will want
+ * diagnose_misspelt_rev == 1 when verifying the first non-rev
+ * argument (which could have been a revision), and
+ * diagnose_misspelt_rev == 0 for the next ones (because we already
+ * saw a filename, there's not ambiguity anymore).
  */
-void verify_filename(const char *prefix, const char *arg)
+void verify_filename(const char *prefix,
+		     const char *arg,
+		     int diagnose_misspelt_rev)
 {
 	if (*arg == '-')
 		die("bad flag '%s' used after filename", arg);
 	if (check_filename(prefix, arg))
 		return;
-	die_verify_filename(prefix, arg);
+	die_verify_filename(prefix, arg, diagnose_misspelt_rev);
 }
 
 /*

t/t1506-rev-parse-diagnosis.sh

@@ -174,7 +174,7 @@ test_expect_success 'relative path when startup_info is NULL' '
 test_expect_success '<commit>:file correctly diagnosed after a pathname' '
 	test_must_fail git rev-parse file.txt HEAD:file.txt 1>actual 2>error &&
 	test_i18ngrep ! "exists on disk" error &&
-	test_i18ngrep "unknown revision or path not in the working tree" error &&
+	test_i18ngrep "no such path in the working tree" error &&
 	cat >expect <<-\EOF &&
 	file.txt
 	HEAD:file.txt