commit 273c61496f88c6495b886acb1041fe57965151da
author Jeff King <peff@peff.net> Mon Sep 24 04:39:55 2018 -0400
committer Junio C Hamano <gitster@pobox.com> Thu Sep 27 09:34:59 2018 -0700
tree 3e4faa8d413bdc0589b69562b09ed09e2cb9a882
parent f6adec4e329ef0e25e14c63b735a5956dc67b8bc

submodule-config: ban submodule paths that start with a dash

We recently banned submodule urls that look like
command-line options. This is the matching change to ban
leading-dash paths.

As with the urls, this should not break any use cases that
currently work. Even with our "--" separator passed to
git-clone, git-submodule.sh gets confused. Without the code
portion of this patch, the clone of "-sub" added in t7417
would yield results like:

    /path/to/git-submodule: 410: cd: Illegal option -s
    /path/to/git-submodule: 417: cd: Illegal option -s
    /path/to/git-submodule: 410: cd: Illegal option -s
    /path/to/git-submodule: 417: cd: Illegal option -s
    Fetched in submodule path '-sub', but it did not contain b56243f8f4eb91b2f1f8109452e659f14dd3fbe4. Direct fetching of that commit failed.

Moreover, naively adding such a submodule doesn't work:

  $ git submodule add $url -sub
  The following path is ignored by one of your .gitignore files:
  -sub

even though there is no such ignore pattern (the test script
hacks around this with a well-placed "git mv").

Unlike leading-dash urls, though, it's possible that such a
path _could_ be useful if we eventually made it work. So
this commit should be seen not as recommending a particular
policy, but rather temporarily closing off a broken and
possibly dangerous code-path. We may revisit this decision
later.

There are two minor differences to the tests in t7416 (that
covered urls):

  1. We don't have a "./-sub" escape hatch to make this
     work, since the submodule code expects to be able to
     match canonical index names to the path field (so you
     are free to add submodule config with that path, but we
     would never actually use it, since an index entry would
     never start with "./").

  2. After this patch, cloning actually succeeds. Since we
     ignore the submodule.*.path value, we fail to find a
     config stanza for our submodule at all, and simply
     treat it as inactive. We still check for the "ignoring"
     message.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>