vcs.rb: copy safe directory configuration

Now revision.tmp will be regenerated always and every times, even if
the recent file exists in the source directory, as far as using git.
On the other hand, VirtualBox mounts shared folders as root, and git
rejects the repository there as dubious ownership.

tool/lib/vcs.rb

@@ -2,6 +2,7 @@
 require 'fileutils'
 require 'optparse'
 require 'pp'
+require 'tempfile'
 
 # This library is used by several other tools/ scripts to detect the current
 # VCS in use (e.g. SVN, Git) or to interact with that VCS.
@@ -419,8 +420,21 @@ class VCS
   end
 
   class GIT < self
-    register(".git") { |path, dir| File.exist?(File.join(path, dir)) }
-    COMMAND = ENV["GIT"] || 'git'
+    register(".git") do |path, dir|
+      SAFE_DIRECTORIES ||=
+        begin
+          command = ENV["GIT"] || 'git'
+          IO.popen(%W"#{command} config --global --get-all safe.directory", &:read).split("\n")
+        rescue
+          command = nil
+          []
+        ensure
+          VCS.dump(SAFE_DIRECTORIES, "safe.directory: ") if $DEBUG
+          COMMAND = command
+        end
+
+      COMMAND and File.exist?(File.join(path, dir))
+    end
 
     def cmd_args(cmds, srcdir = nil)
       (opts = cmds.last).kind_of?(Hash) or cmds << (opts = {})
@@ -459,7 +473,14 @@ class VCS
     def _get_revisions(path, srcdir = nil)
       ref = Branch === path ? path.to_str : 'HEAD'
       gitcmd = [COMMAND]
-      last = cmd_read_at(srcdir, [[*gitcmd, 'rev-parse', ref]]).rstrip
+      last = nil
+      IO.pipe do |r, w|
+        last = cmd_read_at(srcdir, [[*gitcmd, 'rev-parse', ref, err: w]]).rstrip
+        w.close
+        unless r.eof?
+          raise "#{COMMAND} rev-parse failed\n#{r.read.gsub(/^(?=\s*\S)/, '  ')}"
+        end
+      end
       log = cmd_read_at(srcdir, [[*gitcmd, 'log', '-n1', '--date=iso', '--pretty=fuller', *path]])
       changed = log[/\Acommit (\h+)/, 1]
       modified = log[/^CommitDate:\s+(.*)/, 1]
@@ -521,18 +542,34 @@ class VCS
     end
 
     def without_gitconfig
-      envs = %w'HOME XDG_CONFIG_HOME GIT_SYSTEM_CONFIG GIT_CONFIG_SYSTEM'.each_with_object({}) do |v, h|
+      envs = (%w'HOME XDG_CONFIG_HOME' + ENV.keys.grep(/\AGIT_/)).each_with_object({}) do |v, h|
         h[v] = ENV.delete(v)
-        ENV[v] = NullDevice if v.start_with?('GIT_')
       end
+      ENV['GIT_CONFIG_SYSTEM'] = NullDevice
+      ENV['GIT_CONFIG_GLOBAL'] = global_config
       yield
     ensure
       ENV.update(envs)
     end
 
+    def global_config
+      return NullDevice if SAFE_DIRECTORIES.empty?
+      unless @gitconfig
+        @gitconfig = Tempfile.new(%w"vcs_ .gitconfig")
+        @gitconfig.close
+        ENV['GIT_CONFIG_GLOBAL'] = @gitconfig.path
+        SAFE_DIRECTORIES.each do |dir|
+          system(*%W[#{COMMAND} config --global --add safe.directory #{dir}])
+        end
+        VCS.dump(`#{COMMAND} config --global --get-all safe.directory`, "safe.directory: ") if debug?
+      end
+      @gitconfig.path
+    end
+
     def initialize(*)
       super
       @srcdir = File.realpath(@srcdir)
+      @gitconfig = nil
       VCS.dump(@srcdir, "srcdir: ") if debug?
       self
     end