[PATCH/RFC] Emulating symlinks on Windows with file copies

[Patrick Higgins <patrick.higgins@cexp.com>]

Signed-off-by: Patrick Higgins <patrick.higgins@cexp.com>
---

This is a very basic script to test out the idea of using copies to emulate
symlinks on Windows. I don't track any changes in the index yet which seems
necessary as a next step.

Symlinks get deleted and replaced with copies. Existing unchanged copies
are ignored. Copies that have been modified get merged into the target of
the link.

This might have some messy cases that I haven't considered yet, but it seems
like a fairly straightforward way to make a repository containing file
symlinks useful on Windows.

I have not yet started on directories. This technique would probably get
messy with directories. Perhaps junction (reparse) points would be better
for directories?

 git-sync-symlinks.perl |   44 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 44 insertions(+), 0 deletions(-)
 create mode 100755 git-sync-symlinks.perl

diff --git a/git-sync-symlinks.perl b/git-sync-symlinks.perl
new file mode 100755
index 0000000..223ae83
--- /dev/null
+++ b/git-sync-symlinks.perl
@@ -0,0 +1,44 @@
+#!/usr/bin/perl -w
+
+use strict;
+use File::Copy;
+use Fcntl ':mode';
+
+my $filepipe = open(FILELIST, '-|', 'git', 'ls-tree', '-z', '-r', 'HEAD')
+    or die("Cannot call git ls-tree : $!");
+
+local $/ = "\0";
+
+while ( <FILELIST> ) {
+    chomp;
+    if (/^120000 blob ([0-9a-f]{40})\t(.*)$/) {
+        my ($id, $path) = ($1, $2);
+        my $target = `git cat-file blob $id`;
+        chomp($target);
+        my @path_stat = lstat($path);
+        my @target_stat = stat($target);
+        
+        if (S_ISLNK($path_stat[2])) {
+            printf("Copying '%s' to '%s'\n", $target, $path);
+            unlink($path);
+            copy($target, $path);
+        }
+        elsif ($path_stat[7] != $target_stat[7] ||
+               `git hash-object $path` ne `git hash-object $target`)
+        {
+            printf("Merging '%s' to '%s'\n", $path, $target);
+            my @target_parts = split(/\s+/, `git ls-tree HEAD $target`);
+            my $target_id = $target_parts[2];
+            my $original = $target . ".BASE";
+            open(ORIGINAL, '-|', 'git', 'cat-file', 'blob', $target_id);
+            open(ORIGINAL_OUT, '>', $original);
+            while ( <ORIGINAL> ) {
+                print ORIGINAL_OUT $_;
+            }
+            close ORIGINAL_OUT;
+            close ORIGINAL;
+            system('git', 'merge-file', $target, $original, $path);
+        }
+    }
+}
+close FILELIST;
-- 
1.5.6.dirty