improve git repository detectionfix/git-worktree-detection

* configure.in (AC_CONFIG_FILES): $srcdir/.git can be a file pointing
  the real git_dir, such as when the git working tree is a "linked
  working tree" (a working tree created by git-worktree). So use
  git-rev-parse --git-dir to check if $srcdir is the top-level of a git
  repository, not just checking if the $srcdir/.git directory does exist
  or not.
* tool/change_maker.rb: use tool/vcs.rb to detect VCS. This used to have
  its own VCS detection code, while we have tool/vcs.rb.
* tool/vcs.rb (detect): remove code duplication

1 files changed, 12 insertions, 2 deletions

diff --git a/tool/change_maker.rb b/tool/change_maker.rb
index 2bbc275d93..0ed7efd387 100755
--- a/tool/change_maker.rb
+++ b/tool/change_maker.rb
@@ -1,5 +1,8 @@
 #! ./miniruby
 
+$:.unshift(File.expand_path("../../lib", __FILE__))
+require File.expand_path("../vcs", __FILE__)
+
 def diff2index(cmd, *argv)
   lines = []
   path = nil
@@ -22,10 +25,17 @@ def diff2index(cmd, *argv)
   lines.empty? ? nil : lines
 end
 
-if `svnversion` =~ /^\d+/
+vcs = begin
+  VCS.detect(File.dirname(__FILE__))
+rescue VCS::NotFoundError
+  nil
+end
+
+case vcs
+when VCS::SVN
   cmd = "svn diff --diff-cmd=diff -x-pU0"
   change = diff2index(cmd, ARGV)
-elsif File.directory?(".git")
+when VCS::GIT
   cmd = "git diff -U0"
   change = diff2index(cmd, ARGV) || diff2index(cmd, "--cached", ARGV)
 else