git-relink.perl

   1 #!/usr/bin/env perl
   2 # Copyright 2005, Ryan Anderson <ryan@michonline.com>
   3 # Distribution permitted under the GPL v2, as distributed
   4 # by the Free Software Foundation.
   5 # Later versions of the GPL at the discretion of Linus Torvalds
   6 #
   7 # Scan two git object-trees, and hardlink any common objects between them.
   8
   9 use 5.008;
  10 use strict;
  11 use warnings;
  12 use Getopt::Long;
  13
  14 sub get_canonical_form($);
  15 sub do_scan_directory($$$);
  16 sub compare_two_files($$);
  17 sub usage();
  18 sub link_two_files($$);
  19
  20 # stats
  21 my $total_linked = 0;
  22 my $total_already = 0;
  23 my ($linked,$already);
  24
  25 my $fail_on_different_sizes = 0;
  26 my $help = 0;
  27 GetOptions("safe" => \$fail_on_different_sizes,
  28            "help" => \$help);
  29
  30 usage() if $help;
  31
  32 my (@dirs) = @ARGV;
  33
  34 usage() if (!defined $dirs[0] || !defined $dirs[1]);
  35
  36 $_ = get_canonical_form($_) foreach (@dirs);
  37
  38 my $master_dir = pop @dirs;
  39
  40 opendir(D,$master_dir . "objects/")
  41         or die "Failed to open $master_dir/objects/ : $!";
  42
  43 my @hashdirs = grep { ($_ eq 'pack') || /^[0-9a-f]{2}$/ } readdir(D);
  44
  45 foreach my $repo (@dirs) {
  46         $linked = 0;
  47         $already = 0;
  48         printf("Searching '%s' and '%s' for common objects and hardlinking them...\n",
  49                 $master_dir,$repo);
  50
  51         foreach my $hashdir (@hashdirs) {
  52                 do_scan_directory($master_dir, $hashdir, $repo);
  53         }
  54
  55         printf("Linked %d files, %d were already linked.\n",$linked, $already);
  56
  57         $total_linked += $linked;
  58         $total_already += $already;
  59 }
  60
  61 printf("Totals: Linked %d files, %d were already linked.\n",
  62         $total_linked, $total_already);
  63
  64
  65 sub do_scan_directory($$$) {
  66         my ($srcdir, $subdir, $dstdir) = @_;
  67
  68         my $sfulldir = sprintf("%sobjects/%s/",$srcdir,$subdir);
  69         my $dfulldir = sprintf("%sobjects/%s/",$dstdir,$subdir);
  70
  71         opendir(S,$sfulldir)
  72                 or die "Failed to opendir $sfulldir: $!";
  73
  74         foreach my $file (grep(!/\.{1,2}$/, readdir(S))) {
  75                 my $sfilename = $sfulldir . $file;
  76                 my $dfilename = $dfulldir . $file;
  77
  78                 compare_two_files($sfilename,$dfilename);
  79
  80         }
  81         closedir(S);
  82 }
  83
  84 sub compare_two_files($$) {
  85         my ($sfilename, $dfilename) = @_;
  86
  87         # Perl's stat returns relevant information as follows:
  88         # 0 = dev number
  89         # 1 = inode number
  90         # 7 = size
  91         my @sstatinfo = stat($sfilename);
  92         my @dstatinfo = stat($dfilename);
  93
  94         if (@sstatinfo == 0 && @dstatinfo == 0) {
  95                 die sprintf("Stat of both %s and %s failed: %s\n",$sfilename, $dfilename, $!);
  96
  97         } elsif (@dstatinfo == 0) {
  98                 return;
  99         }
 100
 101         if ( ($sstatinfo[0] == $dstatinfo[0]) &&
 102              ($sstatinfo[1] != $dstatinfo[1])) {
 103                 if ($sstatinfo[7] == $dstatinfo[7]) {
 104                         link_two_files($sfilename, $dfilename);
 105
 106                 } else {
 107                         my $err = sprintf("ERROR: File sizes are not the same, cannot relink %s to %s.\n",
 108                                 $sfilename, $dfilename);
 109                         if ($fail_on_different_sizes) {
 110                                 die $err;
 111                         } else {
 112                                 warn $err;
 113                         }
 114                 }
 115
 116         } elsif ( ($sstatinfo[0] == $dstatinfo[0]) &&
 117              ($sstatinfo[1] == $dstatinfo[1])) {
 118                 $already++;
 119         }
 120 }
 121
 122 sub get_canonical_form($) {
 123         my $dir = shift;
 124         my $original = $dir;
 125
 126         die "$dir is not a directory." unless -d $dir;
 127
 128         $dir .= "/" unless $dir =~ m#/$#;
 129         $dir .= ".git/" unless $dir =~ m#\.git/$#;
 130
 131         die "$original does not have a .git/ subdirectory.\n" unless -d $dir;
 132
 133         return $dir;
 134 }
 135
 136 sub link_two_files($$) {
 137         my ($sfilename, $dfilename) = @_;
 138         my $tmpdname = sprintf("%s.old",$dfilename);
 139         rename($dfilename,$tmpdname)
 140                 or die sprintf("Failure renaming %s to %s: %s",
 141                         $dfilename, $tmpdname, $!);
 142
 143         if (! link($sfilename,$dfilename)) {
 144                 my $failtxt = "";
 145                 unless (rename($tmpdname,$dfilename)) {
 146                         $failtxt = sprintf(
 147                                 "Git Repository containing %s is probably corrupted, " .
 148                                 "please copy '%s' to '%s' to fix.\n",
 149                                 $tmpdname, $dfilename);
 150                 }
 151
 152                 die sprintf("Failed to link %s to %s: %s\n%s" .
 153                         $sfilename, $dfilename,
 154                         $!, $dfilename, $failtxt);
 155         }
 156
 157         unlink($tmpdname)
 158                 or die sprintf("Unlink of %s failed: %s\n",
 159                         $dfilename, $!);
 160
 161         $linked++;
 162 }
 163
 164
 165 sub usage() {
 166         print("Usage: git relink [--safe] <dir>... <master_dir> \n");
 167         print("All directories should contain a .git/objects/ subdirectory.\n");
 168         print("Options\n");
 169         print("\t--safe\t" .
 170                 "Stops if two objects with the same hash exist but " .
 171                 "have different sizes.  Default is to warn and continue.\n");
 172         exit(1);
 173 }