Rename some test scripts and describe the naming convention

First digit: "family", e.g. the absolute basics and global stuff (0),
the basic db-side commands (read-tree, write-tree, commit-tree), the
basic working-tree-side commands (checkout-cache, update-cache), the
other basic commands (ls-files), the diff commands, the pull commands,
exporting commands, revision tree commands...

Second digit: the particular command we are testing

Third digit: (optionally) the particular switch or group of switches
we are testing

Freeform part: commandname-details

Described in the README.

	mv t1000-checkout-cache.sh t2000-checkout-cache-clash.sh
	mv t1001-checkout-cache.sh t2001-checkout-cache-clash.sh
	mv t0200-update-cache.sh t2010-update-cache-badpath.sh
	mv t0400-ls-files.sh t3000-ls-files-others.sh
	mv t0500-ls-files.sh t3010-ls-files-killed.sh

t/t2000-checkout-cache-clash.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+#
+# Copyright (c) 2005 Junio C Hamano
+#
+
+test_description='git-checkout-cache test.
+
+This test registers the following filesystem structure in the
+cache:
+
+    path0       - a file
+    path1/file1 - a file in a directory
+
+And then tries to checkout in a work tree that has the following:
+
+    path0/file0 - a file in a directory
+    path1       - a file
+
+The git-checkout-cache command should fail when attempting to checkout
+path0, finding it is occupied by a directory, and path1/file1, finding
+path1 is occupied by a non-directory.  With "-f" flag, it should remove
+the conflicting paths and succeed.
+'
+. ./test-lib.sh
+
+date >path0
+mkdir path1
+date >path1/file1
+
+test_expect_success \
+    'git-update-cache --add various paths.' \
+    'git-update-cache --add path0 path1/file1'
+
+rm -fr path0 path1
+mkdir path0
+date >path0/file0
+date >path1
+
+test_expect_failure \
+    'git-checkout-cache without -f should fail on conflicting work tree.' \
+    'git-checkout-cache -a'
+
+test_expect_success \
+    'git-checkout-cache with -f should succeed.' \
+    'git-checkout-cache -f -a'
+
+test_expect_success \
+    'git-checkout-cache conflicting paths.' \
+    'test -f path0 && test -d path1 && test -f path1/file1'
+
+test_done
+
+