subrepo: disable git and svn subrepos by default (BC) (SEC)

We have a security issue with git subrepos. I'm not sure if svn subrepo is
vulnerable, but it seems not 100% safe to allow writing arbitrary data into
a metadata directory. So for now, only hg subrepo is enabled by default.

Maybe we should improve the help to describe why git/svn subrepos are
disabled.

mercurial/help/config.txt

@@ -1905,7 +1905,7 b' subrepositories feature. See also :hg:`h'
 
     When disallowed, any commands including :hg:`update` will fail if
     subrepositories are involved.
-    (default: `hg, git, svn`)
+    (default: `hg`)
 
 ``templatealias``
 -----------------

mercurial/subrepo.py

@@ -366,7 +366,7 b' def _auditsubrepopath(repo, path):'
         raise error.Abort(_("subrepo '%s' traverses symbolic link") % path)
 
 def _checktype(ui, kind):
-    if kind not in ui.configlist('subrepos', 'allowed', ['hg', 'git', 'svn']):
+    if kind not in ui.configlist('subrepos', 'allowed', ['hg']):
         raise error.Abort(_("subrepo type %s not allowed") % kind,
                           hint=_("see 'hg help config.subrepos' for details"))
     if kind not in types:

tests/test-convert-git.t

@@ -6,6 +6,10 b''
   $ echo "autocrlf = false" >> $HOME/.gitconfig
   $ echo "[extensions]" >> $HGRCPATH
   $ echo "convert=" >> $HGRCPATH
+  $ cat >> $HGRCPATH <<EOF
+  > [subrepos]
+  > allowed = hg, git
+  > EOF
   $ GIT_AUTHOR_NAME='test'; export GIT_AUTHOR_NAME
   $ GIT_AUTHOR_EMAIL='[e-mail]'; export GIT_AUTHOR_EMAIL
   $ GIT_AUTHOR_DATE="2007-01-01 00:00:00 +0000"; export GIT_AUTHOR_DATE

tests/test-mq-subrepo-svn.t

@@ -5,6 +5,8 b''
   > mq =
   > [diff]
   > nodates = 1
+  > [subrepos]
+  > allowed = hg, svn
   > EOF
 
 fn to create new repository, and cd into it

tests/test-subrepo-git.t

@@ -41,7 +41,23 b' add subrepo clone'
   $ echo 's = [git]../gitroot' > .hgsub
   $ git clone -q ../gitroot s
   $ hg add .hgsub
+
+git subrepo is disabled by default
+
   $ hg commit -m 'new git subrepo'
+  abort: subrepo type git not allowed
+  (see 'hg help config.subrepos' for details)
+  [255]
+
+so enable it
+
+  $ cat >> $HGRCPATH <<EOF
+  > [subrepos]
+  > allowed = hg, git
+  > EOF
+
+  $ hg commit -m 'new git subrepo'
+
   $ hg debugsub
   path s
    source   ../gitroot

tests/test-subrepo-svn.t

@@ -57,6 +57,21 b' add first svn sub with leading whitespac'
   $ mkdir subdir
   $ svn co --quiet "$SVNREPOURL"/src subdir/s
   $ hg add .hgsub
+
+svn subrepo is disabled by default
+
+  $ hg ci -m1
+  abort: subrepo type svn not allowed
+  (see 'hg help config.subrepos' for details)
+  [255]
+
+so enable it
+
+  $ cat >> $HGRCPATH <<EOF
+  > [subrepos]
+  > allowed = hg, svn
+  > EOF
+
   $ hg ci -m1
 
 make sure we avoid empty commits (issue2445)