hg-ssh: use shlex for shell-like parsing of SSH_ORIGINAL_COMMAND

The Mercurial ssh protocol is defined as if it was ssh-ing to a shell account on
an ordinary ssh server, and where hg was available in $PATH and it executed
the command "hg -R REPOPATH serve --stdio".

The Mercurial ssh client can in most cases just pass REPOPATH to the shell, but
if it contains unsafe characters the client will have to quote it so the shell
will pass the right -R value to hg. Correct quoting of repopaths was introduced
in d8fa35c28335 and tweaked in 86fc364ca5f8.

hg-ssh doesn't create the command via a shell and used a simple parser instead.
It worked fine for simple paths without any quoting, but if any kind of quoting
was used it failed to parse the command like the shell would do it.

This makes hg-ssh behave more like a normal shell with hg in the path would do.

contrib/hg-ssh

@@ -31,15 +31,20 b' from mercurial import demandimport; dema'
 
 from mercurial import dispatch
 
-import sys, os
+import sys, os, shlex
 
 cwd = os.getcwd()
 allowed_paths = [os.path.normpath(os.path.join(cwd, os.path.expanduser(path)))
                  for path in sys.argv[1:]]
 orig_cmd = os.getenv('SSH_ORIGINAL_COMMAND', '?')
+try:
+    cmdargv = shlex.split(orig_cmd)
+except ValueError, e:
+    sys.stderr.write("Illegal command %r: %s\n" % (orig_cmd, e))
+    sys.exit(-1)
 
-if orig_cmd.startswith('hg -R ') and orig_cmd.endswith(' serve --stdio'):
-    path = orig_cmd[6:-14]
+if cmdargv[:2] == ['hg', '-R'] and cmdargv[3:] == ['serve', '--stdio']:
+    path = cmdargv[2]
     repo = os.path.normpath(os.path.join(cwd, os.path.expanduser(path)))
     if repo in allowed_paths:
         dispatch.dispatch(dispatch.request(['-R', repo, 'serve', '--stdio']))

tests/test-ssh.t

@@ -275,6 +275,19 b' Test remote paths with spaces (issue2983'
   $ hg id --ssh "python $TESTDIR/dummyssh" "ssh://user@dummy/a repo"
   3fb238f49e8c
 
+Test hg-ssh:
+
+  $ SSH_ORIGINAL_COMMAND="'hg' -R 'a repo' serve --stdio" hg id --ssh "python \"$TESTDIR\"/../contrib/hg-ssh \"$TESTTMP/a repo\"" "ssh://user@dummy/a repo"
+  3fb238f49e8c
+  $ SSH_ORIGINAL_COMMAND="'hg' -R 'a repo' serve --stdio" hg id --ssh "python \"$TESTDIR\"/../contrib/hg-ssh \"$TESTTMP\"" "ssh://user@dummy/a repo"
+  remote: Illegal repository '$TESTTMP/a repo'
+  abort: no suitable response from remote hg!
+  [255]
+  $ SSH_ORIGINAL_COMMAND="'hg' -R 'a'repo' serve --stdio" hg id --ssh "python \"$TESTDIR\"/../contrib/hg-ssh \"$TESTTMP\"" "ssh://user@dummy/a repo"
+  remote: Illegal command "'hg' -R 'a'repo' serve --stdio": No closing quotation
+  abort: no suitable response from remote hg!
+  [255]
+
   $ cat dummylog
   Got arguments 1:user@dummy 2:hg -R nonexistent serve --stdio
   Got arguments 1:user@dummy 2:hg -R /$TESTTMP/nonexistent serve --stdio