public-inbox-index: resolve git directory if run inside one

I often forget to pass the correct path to a git directory
or run from inside one.  Fortunately git is script-friendly
and allows easily resolving the correct GIT_DIR path.

1 files changed, 33 insertions, 2 deletions

diff --git a/public-inbox-index b/public-inbox-index
index f39ad9e1..44814e3f 100755
--- a/public-inbox-index
+++ b/public-inbox-index
@@ -15,11 +15,42 @@ if ($@) {
         print STDERR "Search::Xapian required for $0\n";
         exit 1;
 }
+my @dirs;
+
+sub resolve_git_dir {
+        my ($cd) = @_;
+        my @cmd = qw(git rev-parse --git-dir);
+        my $cmd = join(' ', @cmd);
+        my $pid = open my $fh, '-|';
+        defined $pid or die "forking $cmd failed: $!\n";
+        if ($pid == 0) {
+                if (defined $cd) {
+                        chdir $cd or die "chdir $cd failed: $!\n";
+                }
+                exec @cmd;
+                die "Failed to exec $cmd: $!\n";
+        } else {
+                my $dir = eval {
+                        local $/;
+                        <$fh>;
+                };
+                close $fh or die "error in $cmd: $!\n";
+                chomp $dir;
+                return $cd if ($dir eq '.' && defined $cd);
+                $dir;
+        }
+}
+
+if (@ARGV) {
+        @dirs = map { resolve_git_dir($_) } @ARGV;
+} else {
+        @dirs = (resolve_git_dir());
+}
 
 sub usage { print STDERR "Usage: $usage\n"; exit 1 }
-usage() unless @ARGV;
+usage() unless @dirs;
 
-foreach my $dir (@ARGV) {
+foreach my $dir (@dirs) {
         index_dir($dir);
 }