[git-llvm] Only use --force-interactive when supported

The --force-interactive option was introduced in SVN 1.8, and trying to
pass it to older SVN clients causes an error; CentOS 7 includes SVN 1.7,
for example, so this makes `git llvm` not usable out of the box. Older
clients would be interactive by default anyway [1], so just don't pass
the option if it's not supported.

An alternative would be to check the version instead of checking the
help text, but I think directly detecting the presence of the option is
more direct.

[1] http://svn.apache.org/viewvc?view=revision&revision=1424037

Differential Revision: https://reviews.llvm.org/D59161

llvm-svn: 355782

utils/git-svn/git-llvm

@@ -345,7 +345,10 @@ def svn_push_one_rev(svn_repo, rev, dry_run):
     # Now we're ready to commit.
     commit_msg = git('show', '--pretty=%B', '--quiet', rev)
     if not dry_run:
-        log(svn(svn_repo, 'commit', '-m', commit_msg, '--force-interactive'))
+        commit_args = ['commit', '-m', commit_msg]
+        if '--force-interactive' in svn(svn_repo, 'commit', '--help'):
+            commit_args.append('--force-interactive')
+        log(svn(svn_repo, *commit_args))
         log('Committed %s to svn.' % rev)
     else:
         log("Would have committed %s to svn, if this weren't a dry run." % rev)