made the pack completely portable and wrote relevent bat files to go with it

gitportable/mingw64/share/doc/git-doc/git-get-tar-commit-id.adoc

@@ -0,0 +1,30 @@
+git-get-tar-commit-id(1)
+========================
+
+NAME
+----
+git-get-tar-commit-id - Extract commit ID from an archive created using git-archive
+
+
+SYNOPSIS
+--------
+[verse]
+'git get-tar-commit-id'
+
+
+DESCRIPTION
+-----------
+
+Read a tar archive created by 'git archive' from the standard input
+and extract the commit ID stored in it.  It reads only the first
+1024 bytes of input, thus its runtime is not influenced by the size
+of the tar archive very much.
+
+If no commit ID is found, 'git get-tar-commit-id' quietly exits with a
+return code of 1.  This can happen if the archive had not been created
+using 'git archive' or if the first parameter of 'git archive' had been
+a tree ID instead of a commit ID or tag.
+
+GIT
+---
+Part of the linkgit:git[1] suite