cvsimport: cleanup commit function

This change attempts to clean up the commit function to make it a bit
easier to read (or at least the first half of it). It also improves
robustness and performance. Specifically:
  - report get_headref errors on opening ref unless the error is ENOENT
  - use regex to check for sha1 instead of length
  - use lexically scoped filehandles which get cleaned up automagically
  - check for error on both 'print' and 'close' (since output is buffered)
  - avoid "fork, do some perl, then exec" in commit(). It's not necessary,
    and we probably end up COW'ing parts of the perl process. Plus the code
    is much smaller because we can use open2()
  - avoid calling strftime over and over (mainly a readability cleanup)

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/git-cvsimport.perl b/git-cvsimport.perl
index 90ca018..f0e4d24 100755 (executable)
--- a/git-cvsimport.perl
+++ b/git-cvsimport.perl
@@ -23,7 +23,7 @@ use File::Basename qw(basename dirname);
 use Time::Local;
 use IO::Socket;
 use IO::Pipe;
-use POSIX qw(strftime dup2);
+use POSIX qw(strftime dup2 :errno_h);
 use IPC::Open2;
 
 $SIG{'PIPE'}="IGNORE";
@@ -429,22 +429,25 @@ sub getwd() {
        return $pwd;
 }
 
+sub is_sha1 {
+       my $s = shift;
+       return $s =~ /^[a-f0-9]{40}$/;
+}
 
-sub get_headref($$) {
+sub get_headref ($$) {
     my $name    = shift;
     my $git_dir = shift; 
-    my $sha;
     
-    if (open(C,"$git_dir/refs/heads/$name")) {
-       chomp($sha = <C>);
-       close(C);
-       length($sha) == 40
-           or die "Cannot get head id for $name ($sha): $!\n";
+    my $f = "$git_dir/refs/heads/$name";
+    if(open(my $fh, $f)) {
+           chomp(my $r = <$fh>);
+           is_sha1($r) or die "Cannot get head id for $name ($r): $!";
+           return $r;
     }
-    return $sha;
+    die "unable to open $f: $!" unless $! == POSIX::ENOENT;
+    return undef;
 }
 
-
 -d $git_tree
        or mkdir($git_tree,0777)
        or die "Could not create $git_tree: $!";
@@ -561,90 +564,67 @@ unless($pid) {
 
 my $state = 0;
 
-my($patchset,$date,$author_name,$author_email,$branch,$ancestor,$tag,$logmsg);
-my(@old,@new,@skipped);
-sub commit {
-       my $pid;
-
+sub update_index (\@\@) {
+       my $old = shift;
+       my $new = shift;
        open(my $fh, '|-', qw(git-update-index -z --index-info))
                or die "unable to open git-update-index: $!";
        print $fh
                (map { "0 0000000000000000000000000000000000000000\t$_\0" }
-                       @old),
+                       @$old),
                (map { '100' . sprintf('%o', $_->[0]) . " $_->[1]\t$_->[2]\0" }
-                       @new)
+                       @$new)
                or die "unable to write to git-update-index: $!";
        close $fh
                or die "unable to write to git-update-index: $!";
        $? and die "git-update-index reported error: $?";
-       @old = @new = ();
+}
 
-       $pid = open(C,"-|");
-       die "Cannot fork: $!" unless defined $pid;
-       unless($pid) {
-               exec("git-write-tree");
-               die "Cannot exec git-write-tree: $!\n";
-       }
-       chomp(my $tree = <C>);
-       length($tree) == 40
-               or die "Cannot get tree id ($tree): $!\n";
-       close(C)
+sub write_tree () {
+       open(my $fh, '-|', qw(git-write-tree))
+               or die "unable to open git-write-tree: $!";
+       chomp(my $tree = <$fh>);
+       is_sha1($tree)
+               or die "Cannot get tree id ($tree): $!";
+       close($fh)
                or die "Error running git-write-tree: $?\n";
        print "Tree ID $tree\n" if $opt_v;
+       return $tree;
+}
 
-       my $parent = "";
-       if(open(C,"$git_dir/refs/heads/$last_branch")) {
-               chomp($parent = <C>);
-               close(C);
-               length($parent) == 40
-                       or die "Cannot get parent id ($parent): $!\n";
-               print "Parent ID $parent\n" if $opt_v;
-       }
-
-       my $pr = IO::Pipe->new() or die "Cannot open pipe: $!\n";
-       my $pw = IO::Pipe->new() or die "Cannot open pipe: $!\n";
-       $pid = fork();
-       die "Fork: $!\n" unless defined $pid;
-       unless($pid) {
-               $pr->writer();
-               $pw->reader();
-               open(OUT,">&STDOUT");
-               dup2($pw->fileno(),0);
-               dup2($pr->fileno(),1);
-               $pr->close();
-               $pw->close();
-
-               my @par = ();
-               @par = ("-p",$parent) if $parent;
-
-               # loose detection of merges
-               # based on the commit msg
-               foreach my $rx (@mergerx) {
-                       if ($logmsg =~ $rx) {
-                               my $mparent = $1;
-                               if ($mparent eq 'HEAD') { $mparent = $opt_o };
-                               if ( -e "$git_dir/refs/heads/$mparent") {
-                                       $mparent = get_headref($mparent, $git_dir);
-                                       push @par, '-p', $mparent;
-                                       print OUT "Merge parent branch: $mparent\n" if $opt_v;
-                               }
-                       }
+my($patchset,$date,$author_name,$author_email,$branch,$ancestor,$tag,$logmsg);
+my(@old,@new,@skipped);
+sub commit {
+       update_index(@old, @new);
+       @old = @new = ();
+       my $tree = write_tree();
+       my $parent = get_headref($last_branch, $git_dir);
+       print "Parent ID " . ($parent ? $parent : "(empty)") . "\n" if $opt_v;
+
+       my @commit_args;
+       push @commit_args, ("-p", $parent) if $parent;
+
+       # loose detection of merges
+       # based on the commit msg
+       foreach my $rx (@mergerx) {
+               next unless $logmsg =~ $rx && $1;
+               my $mparent = $1 eq 'HEAD' ? $opt_o : $1;
+               if(my $sha1 = get_headref($mparent, $git_dir)) {
+                       push @commit_args, '-p', $mparent;
+                       print "Merge parent branch: $mparent\n" if $opt_v;
                }
-
-               exec("env",
-                       "GIT_AUTHOR_NAME=$author_name",
-                       "GIT_AUTHOR_EMAIL=$author_email",
-                       "GIT_AUTHOR_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
-                       "GIT_COMMITTER_NAME=$author_name",
-                       "GIT_COMMITTER_EMAIL=$author_email",
-                       "GIT_COMMITTER_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
-                       "git-commit-tree", $tree,@par);
-               die "Cannot exec git-commit-tree: $!\n";
-
-               close OUT;
        }
-       $pw->writer();
-       $pr->reader();
+
+       my $commit_date = strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date));
+       my $pid = open2(my $commit_read, my $commit_write,
+               'env',
+               "GIT_AUTHOR_NAME=$author_name",
+               "GIT_AUTHOR_EMAIL=$author_email",
+               "GIT_AUTHOR_DATE=$commit_date",
+               "GIT_COMMITTER_NAME=$author_name",
+               "GIT_COMMITTER_EMAIL=$author_email",
+               "GIT_COMMITTER_DATE=$commit_date",
+               'git-commit-tree', $tree, @commit_args);
 
        # compatibility with git2cvs
        substr($logmsg,32767) = "" if length($logmsg) > 32767;
@@ -656,16 +636,14 @@ sub commit {
            @skipped = ();
        }
 
-       print $pw "$logmsg\n"
+       print($commit_write "$logmsg\n") && close($commit_write)
                or die "Error writing to git-commit-tree: $!\n";
-       $pw->close();
 
-       print "Committed patch $patchset ($branch ".strftime("%Y-%m-%d %H:%M:%S",gmtime($date)).")\n" if $opt_v;
-       chomp(my $cid = <$pr>);
-       length($cid) == 40
-               or die "Cannot get commit id ($cid): $!\n";
+       print "Committed patch $patchset ($branch $commit_date)\n" if $opt_v;
+       chomp(my $cid = <$commit_read>);
+       is_sha1($cid) or die "Cannot get commit id ($cid): $!\n";
        print "Commit ID $cid\n" if $opt_v;
-       $pr->close();
+       close($commit_read);
 
        waitpid($pid,0);
        die "Error running git-commit-tree: $?\n" if $?;