More permissive "git-rm --cached" behavior without -f.

In the previous behavior, "git-rm --cached" (without -f) had the same
restriction as "git-rm". This forced the user to use the -f flag in
situations which weren't actually dangerous, like:

$ git add foo           # oops, I didn't want this
$ git rm --cached foo   # back to initial situation

Previously, the index had to match the file *and* the HEAD. With
--cached, the index must now match the file *or* the HEAD. The behavior
without --cached is unchanged, but provides better error messages.

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

Documentation/git-rm.txt

@@ -14,7 +14,8 @@ DESCRIPTION
 Remove files from the working tree and from the index.  The
 files have to be identical to the tip of the branch, and no
 updates to its contents must have been placed in the staging
-area (aka index).
+area (aka index).  When --cached is given, the staged content has to
+match either the tip of the branch *or* the file on disk.
 
 
 OPTIONS

builtin-rm.c

@@ -46,7 +46,7 @@ static int remove_file(const char *name)
 	return ret;
 }
 
-static int check_local_mod(unsigned char *head)
+static int check_local_mod(unsigned char *head, int index_only)
 {
 	/* items in list are already sorted in the cache order,
 	 * so we could do this a lot more efficiently by using
@@ -65,6 +65,8 @@ static int check_local_mod(unsigned char *head)
 		const char *name = list.name[i];
 		unsigned char sha1[20];
 		unsigned mode;
+		int local_changes = 0;
+		int staged_changes = 0;
 
 		pos = cache_name_pos(name, strlen(name));
 		if (pos < 0)
@@ -87,14 +89,32 @@ static int check_local_mod(unsigned char *head)
 			continue;
 		}
 		if (ce_match_stat(ce, &st, 0))
-			errs = error("'%s' has local modifications "
-				     "(hint: try -f)", ce->name);
+			local_changes = 1;
 		if (no_head
 		     || get_tree_entry(head, name, sha1, &mode)
 		     || ce->ce_mode != create_ce_mode(mode)
 		     || hashcmp(ce->sha1, sha1))
-			errs = error("'%s' has changes staged in the index "
-				     "(hint: try -f)", name);
+			staged_changes = 1;
+
+		if (local_changes && staged_changes)
+			errs = error("'%s' has staged content different "
+				     "from both the file and the HEAD\n"
+				     "(use -f to force removal)", name);
+		else if (!index_only) {
+			/* It's not dangerous to git-rm --cached a
+			 * file if the index matches the file or the
+			 * HEAD, since it means the deleted content is
+			 * still available somewhere.
+			 */
+			if (staged_changes)
+				errs = error("'%s' has changes staged in the index\n"
+					     "(use --cached to keep the file, "
+					     "or -f to force removal)", name);
+			if (local_changes)
+				errs = error("'%s' has local modifications\n"
+					     "(use --cached to keep the file, "
+					     "or -f to force removal)", name);
+		}
 	}
 	return errs;
 }
@@ -192,7 +212,7 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 		unsigned char sha1[20];
 		if (get_sha1("HEAD", sha1))
 			hashclr(sha1);
-		if (check_local_mod(sha1))
+		if (check_local_mod(sha1, index_only))
 			exit(1);
 	}
 

t/t3600-rm.sh

@@ -45,6 +45,40 @@ test_expect_success \
     'Test that git rm foo succeeds' \
     'git rm --cached foo'
 
+test_expect_success \
+    'Test that git rm --cached foo succeeds if the index matches the file' \
+    'echo content > foo
+     git add foo
+     git rm --cached foo'
+
+test_expect_success \
+    'Test that git rm --cached foo succeeds if the index matches the file' \
+    'echo content > foo
+     git add foo
+     git commit -m foo
+     echo "other content" > foo
+     git rm --cached foo'
+
+test_expect_failure \
+    'Test that git rm --cached foo fails if the index matches neither the file nor HEAD' \
+    'echo content > foo
+     git add foo
+     git commit -m foo
+     echo "other content" > foo
+     git add foo
+     echo "yet another content" > foo
+     git rm --cached foo'
+
+test_expect_success \
+    'Test that git rm --cached -f foo works in case where --cached only did not' \
+    'echo content > foo
+     git add foo
+     git commit -m foo
+     echo "other content" > foo
+     git add foo
+     echo "yet another content" > foo
+     git rm --cached -f foo'
+
 test_expect_success \
     'Post-check that foo exists but is not in index after git rm foo' \
     '[ -f foo ] && ! git ls-files --error-unmatch foo'