tar archive frontend for fast-import.

This is an example fast-import frontend, in less than 100 lines
of Perl.  It accepts one or more tar archives on the command line,
passes them through gzcat/bzcat/zcat if necessary, parses out the
individual file headers and feeds all contained data to fast-import.
No temporary files are involved.

Each tar is treated as one commit, with the commit timestamp coming
from the oldest file modification date found within the tar.

Each tar is also tagged with an annotated tag, using the basename
of the tar file as the name of the tag.

Currently symbolic links and hard links are not handled by the
importer.  The file checksums are also not verified.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

diff --git a/contrib/fast-import/import-tars.perl b/contrib/fast-import/import-tars.perl
new file mode 100755 (executable)
index 0000000..26c42c9
--- /dev/null
+++ b/contrib/fast-import/import-tars.perl
@@ -0,0 +1,105 @@
+#!/usr/bin/perl
+
+## tar archive frontend for git-fast-import
+##
+## For example:
+##
+##  mkdir project; cd project; git init
+##  perl import-tars.perl *.tar.bz2
+##  git whatchanged import-tars
+##
+
+use strict;
+die "usage: import-tars *.tar.{gz,bz2,Z}\n" unless @ARGV;
+
+my $branch_name = 'import-tars';
+my $branch_ref = "refs/heads/$branch_name";
+my $committer_name = 'T Ar Creator';
+my $committer_email = 'tar@example.com';
+
+open(FI, '|-', 'git', 'fast-import', '--quiet')
+       or die "Unable to start git fast-import: $!\n";
+foreach my $tar_file (@ARGV)
+{
+       $tar_file =~ m,([^/]+)$,;
+       my $tar_name = $1;
+
+       if ($tar_name =~ s/\.(tar\.gz|tgz)$//) {
+               open(I, '-|', 'gzcat', $tar_file) or die "Unable to gzcat $tar_file: $!\n";
+       } elsif ($tar_name =~ s/\.(tar\.bz2|tbz2)$//) {
+               open(I, '-|', 'bzcat', $tar_file) or die "Unable to bzcat $tar_file: $!\n";
+       } elsif ($tar_name =~ s/\.tar\.Z$//) {
+               open(I, '-|', 'zcat', $tar_file) or die "Unable to zcat $tar_file: $!\n";
+       } elsif ($tar_name =~ s/\.tar$//) {
+               open(I, $tar_file) or die "Unable to open $tar_file: $!\n";
+       } else {
+               die "Unrecognized compression format: $tar_file\n";
+       }
+
+       my $commit_time = 0;
+       my $next_mark = 1;
+       my $have_top_dir = 1;
+       my ($top_dir, %files);
+
+       while (read(I, $_, 512) == 512) {
+               my ($name, $mode, $uid, $gid, $size, $mtime,
+                       $chksum, $typeflag, $linkname, $magic,
+                       $version, $uname, $gname, $devmajor, $devminor,
+                       $prefix) = unpack 'Z100 Z8 Z8 Z8 Z12 Z12
+                       Z8 Z1 Z100 Z6
+                       Z2 Z32 Z32 Z8 Z8 Z*', $_;
+               last unless $name;
+               $mode = oct $mode;
+               $size = oct $size;
+               $mtime = oct $mtime;
+               next if $mode & 0040000;
+
+               print FI "blob\n", "mark :$next_mark\n", "data $size\n";
+               while ($size > 0 && read(I, $_, 512) == 512) {
+                       print FI substr($_, 0, $size);
+                       $size -= 512;
+               }
+               print FI "\n";
+
+               my $path = "$prefix$name";
+               $files{$path} = [$next_mark++, $mode];
+
+               $commit_time = $mtime if $mtime > $commit_time;
+               $path =~ m,^([^/]+)/,;
+               $top_dir = $1 unless $top_dir;
+               $have_top_dir = 0 if $top_dir ne $1;
+       }
+
+       print FI <<EOF;
+commit $branch_ref
+committer $committer_name <$committer_email> $commit_time +0000
+data <<END_OF_COMMIT_MESSAGE
+Imported from $tar_file.
+END_OF_COMMIT_MESSAGE
+
+deleteall
+EOF
+
+       foreach my $path (keys %files)
+       {
+               my ($mark, $mode) = @{$files{$path}};
+               my $git_mode = 0644;
+               $git_mode |= 0700 if $mode & 0111;
+               $path =~ s,^([^/]+)/,, if $have_top_dir;
+               printf FI "M %o :%i %s\n", $git_mode, $mark, $path;
+       }
+       print FI "\n";
+
+       print FI <<EOF;
+tag $tar_name
+from $branch_ref
+tagger $committer_name <$committer_email> $commit_time +0000
+data <<END_OF_TAG_MESSAGE
+Package $tar_name
+END_OF_TAG_MESSAGE
+
+EOF
+
+       close I;
+}
+close FI;