pathspec: give better message for submodule related pathspec error

Every once in a while someone complains to the mailing list to have
run into this weird assertion[1]. The usual response from the mailing
list is link to old discussions[2], and acknowledging the problem
stating it is known.

This patch accomplishes two things:

1. Switch assert() to die("BUG") to give a more readable message.

2. Take one of the cases where we hit a BUG and turn it into a normal
"there was something wrong with the input" message.

This assertion triggered for cases where there wasn't a programming
bug, but just bogus input. In particular, if the user asks for a
pathspec that is inside a submodule, we shouldn't assert() or
die("BUG"); we should tell the user their request is bogus.

The only reason we did not check for it, is the expensive nature
of such a check, so callers avoid setting the flag
PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE. However when we die due
to bogus input, the expense of CPU cycles spent outweighs the user
wondering what went wrong, so run that check unconditionally before
dying with a more generic error message.

Note: There is a case (e.g. "git -C submodule add .") in which we call
strip_submodule_slash_expensive, as git-add requests it via the flag
PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE, but the assert used to
trigger nevertheless, because the flag PATHSPEC_LITERAL was not set,
such that we executed

if (item->nowildcard_len < prefixlen)
item->nowildcard_len = prefixlen;

and prefixlen was not adapted (e.g. it was computed from "submodule/")
So in the die_inside_submodule_path function we also need handle paths,
that were stripped before, i.e. are the exact submodule path. This
is why the conditions in die_inside_submodule_path are slightly
different than in strip_submodule_slash_expensive.

[1] https://www.google.com/search?q=item-%3Enowildcard_len
[2] http://git.661346.n2.nabble.com/assert-failed-in-submodule-edge-case-td7628687.html
https://www.spinics.net/lists/git/msg249473.html

Helped-by: Jeff King <peff@peff.net>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/pathspec.c b/pathspec.c
index ff2509ddd1519b19090bd4df6ed7bfdb4909d499..7ababb315944d5536ec251b19937beef5def2538 100644 (file)
--- a/pathspec.c
+++ b/pathspec.c
@@ -296,6 +296,27 @@ static void strip_submodule_slash_expensive(struct pathspec_item *item)
        }
 }
 
        }
 }
 

+static void die_inside_submodule_path(struct pathspec_item *item)
+{
+       int i;
+
+       for (i = 0; i < active_nr; i++) {
+               struct cache_entry *ce = active_cache[i];
+               int ce_len = ce_namelen(ce);
+
+               if (!S_ISGITLINK(ce->ce_mode))
+                       continue;
+
+               if (item->len < ce_len ||
+                   !(item->match[ce_len] == '/' || item->match[ce_len] == '\0') ||
+                   memcmp(ce->name, item->match, ce_len))
+                       continue;
+
+               die(_("Pathspec '%s' is in submodule '%.*s'"),
+                   item->original, ce_len, ce->name);
+       }
+}
+

 /*
  * Perform the initialization of a pathspec_item based on a pathspec element.
  */
 /*
  * Perform the initialization of a pathspec_item based on a pathspec element.
  */


@@ -391,8 +412,18 @@ static void init_pathspec_item(struct pathspec_item *item, unsigned flags,
        }
 
        /* sanity checks, pathspec matchers assume these are sane */
        }
 
        /* sanity checks, pathspec matchers assume these are sane */

-       assert(item->nowildcard_len <= item->len &&
-              item->prefix         <= item->len);
+       if (item->nowildcard_len > item->len ||
+           item->prefix         > item->len) {
+               /*
+                * This case can be triggered by the user pointing us to a
+                * pathspec inside a submodule, which is an input error.
+                * Detect that here and complain, but fallback in the
+                * non-submodule case to a BUG, as we have no idea what
+                * would trigger that.
+                */
+               die_inside_submodule_path(item);
+               die ("BUG: item->nowildcard_len > item->len || item->prefix > item->len)");
+       }

 }
 
 static int pathspec_item_cmp(const void *a_, const void *b_)
 }
 
 static int pathspec_item_cmp(const void *a_, const void *b_)

diff --git a/t/t6134-pathspec-in-submodule.sh b/t/t6134-pathspec-in-submodule.sh
new file mode 100755 (executable)
index 0000000..fd401ca
--- /dev/null
+++ b/t/t6134-pathspec-in-submodule.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+
+test_description='test case exclude pathspec'
+
+. ./test-lib.sh
+
+test_expect_success 'setup a submodule' '
+       test_create_repo pretzel &&
+       : >pretzel/a &&
+       git -C pretzel add a &&
+       git -C pretzel commit -m "add a file" -- a &&
+       git submodule add ./pretzel sub &&
+       git commit -a -m "add submodule" &&
+       git submodule deinit --all
+'
+
+cat <<EOF >expect
+fatal: Pathspec 'sub/a' is in submodule 'sub'
+EOF
+
+test_expect_success 'error message for path inside submodule' '
+       echo a >sub/a &&
+       test_must_fail git add sub/a 2>actual &&
+       test_cmp expect actual
+'
+
+cat <<EOF >expect
+fatal: Pathspec '.' is in submodule 'sub'
+EOF
+
+test_expect_success 'error message for path inside submodule from within submodule' '
+       test_must_fail git -C sub add . 2>actual &&
+       test_cmp expect actual
+'
+
+test_done