Add a script that checks if commits maintained literal copies

When updating, say, gcc, it is possible that some files were updated, but
others were left as-are.  This is particularly wrong with files that are
supposed to be hardlinks (but that are actually copies due to being
checked out by Git).

Provide a script that checks if commits left literal copies intact.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

share/msysGit/check-literal-copies.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+# This script will check for files that were literal copies in the
+# parents of the given commits, but are no literal copies currently
+# (ignoring those files that do no longer exist).
+
+# Use it like this:
+#
+#	$0 $(git rev-list HEAD -- mingw/bin/gcc.exe)
+#
+# This would check that literal copies were maintained in all the commits
+# in the current branch that touched mingw/bin/gcc.exe.
+
+for rev in "$@"
+do
+	# Ignore initial commit
+	git rev-parse -q --verify $rev^ > /dev/null || continue
+
+	for f in $(git diff --name-only --diff-filter=RDM $rev^!)
+	do
+		test -f $f || continue
+		sha1=$(git rev-parse $rev^:$f)
+		matches="$(git ls-tree -r $rev^ | grep $sha1)"
+		test 1 -lt $(echo "$matches" | wc -l) && {
+			for f2 in $(echo "$matches" | sed "s/.*	//")
+			do
+				test -f $f2 || continue
+				cmp $f $f2 || echo "$f != $f2"
+			done
+		}
+	done
+done