[PATCH] Diff overhaul, adding half of copy detection.

This introduces the diff-core, the layer between the diff-tree
family and the external diff interface engine.  The calls to the
interface diff-tree family uses (diff_change and diff_addremove)
have not changed and will not change.  The purpose of the
diff-core layer is to provide an infrastructure to transform the
set of differences sent from the applications, before sending
them to the external diff interface.

The recently introduced rename detection code has been rewritten
to use the diff-core facility.  When applications send in
separate creates and deletes, matching ones are transformed into
a single rename-and-edit diff, and sent out to the external diff
interface as such.

This patch also enhances the rename detection code further to be
able to detect copies.  Currently this happens only as long as
copy sources appear as part of the modified files, but there
already is enough provision for callers to report unmodified
files to diff-core, so that they can be also used as copy source
candidates.  Extending the callers this way will be done in a
separate patch.

Please see and marvel at how well this works by trying out the
newly added t/t4003-diff-rename-1.sh test script.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 96 insertions, 3 deletions

diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 6fb7b1a12..1a3a51122 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh
@@ -32,7 +32,7 @@ test_expect_success \
 find .git/objects -type d -print >full-of-directories
 test_expect_success \
     '.git/objects should have 256 subdirectories.' \
-    'test $(cat full-of-directories | wc -l) = 257'
+    'test $(wc -l < full-of-directories) = 257'
 
 ################################################################
 # Basics of the basics
diff --git a/t/t4001-diff-rename.sh b/t/t4001-diff-rename.sh
index 065ddb71a..933a5bfc6 100755
--- a/t/t4001-diff-rename.sh
+++ b/t/t4001-diff-rename.sh
@@ -31,7 +31,7 @@ test_expect_success \
 
 test_expect_success \
     'write that tree.' \
-    'tree=$(git-write-tree)'
+    'tree=$(git-write-tree) && echo $tree'
 
 sed -e 's/line/Line/' <path0 >path1
 rm -f path0
@@ -61,6 +61,6 @@ EOF
 
 test_expect_success \
     'validate the output.' \
-    'diff -I "rename similarity.*" >/dev/null current expected'
+    'diff -I "similarity.*" >/dev/null current expected'
 
 test_done
diff --git a/t/t4003-diff-rename-1.sh b/t/t4003-diff-rename-1.sh
new file mode 100644
index 000000000..20d8ac5f8
--- /dev/null
+++ b/t/t4003-diff-rename-1.sh
@@ -0,0 +1,93 @@
+#!/bin/sh
+#
+# Copyright (c) 2005 Junio C Hamano
+#
+
+test_description='More rename detection
+
+'
+. ./test-lib.sh
+
+test_expect_success \
+    'prepare reference tree' \
+    'cat ../../COPYING >COPYING &&
+    git-update-cache --add COPYING &&
+    tree=$(git-write-tree) &&
+    echo $tree'
+
+test_expect_success \
+    'prepare work tree' \
+    'sed -e 's/HOWEVER/However/' <COPYING >COPYING.1 &&
+    sed -e 's/GPL/G.P.L/g' <COPYING >COPYING.2 &&
+    rm -f COPYING &&
+    git-update-cache --add --remove COPYING COPYING.?'
+
+GIT_DIFF_OPTS=-u0 git-diff-cache -M $tree |
+sed -e 's/\([0-9][0-9]*\)/#/g' >current &&
+cat >expected <<\EOF
+diff --git a/COPYING b/COPYING.#
+similarity index #%
+copy from COPYING
+copy to COPYING.#
+--- a/COPYING
++++ b/COPYING.#
+@@ -# +# @@
+- HOWEVER, in order to allow a migration to GPLv# if that seems like
++ However, in order to allow a migration to GPLv# if that seems like
+diff --git a/COPYING b/COPYING.#
+similarity index #%
+rename old COPYING
+rename new COPYING.#
+--- a/COPYING
++++ b/COPYING.#
+@@ -# +# @@
+- Note that the only valid version of the GPL as far as this project
++ Note that the only valid version of the G.P.L as far as this project
+@@ -# +# @@
+- HOWEVER, in order to allow a migration to GPLv# if that seems like
++ HOWEVER, in order to allow a migration to G.P.Lv# if that seems like
+@@ -# +# @@
+-	This file is licensed under the GPL v#, or a later version
++	This file is licensed under the G.P.L v#, or a later version
+EOF
+
+test_expect_success \
+    'validate output from rename/copy detection' \
+    'diff -u current expected'
+
+test_expect_success \
+    'prepare work tree again' \
+    'mv COPYING.2 COPYING &&
+     git-update-cache --add --remove COPYING COPYING.1'
+
+GIT_DIFF_OPTS=-u0 git-diff-cache -C $tree |
+sed -e 's/\([0-9][0-9]*\)/#/g' >current
+cat >expected <<\EOF
+diff --git a/COPYING b/COPYING.#
+similarity index #%
+copy from COPYING
+copy to COPYING.#
+--- a/COPYING
++++ b/COPYING.#
+@@ -# +# @@
+- HOWEVER, in order to allow a migration to GPLv# if that seems like
++ However, in order to allow a migration to GPLv# if that seems like
+diff --git a/COPYING b/COPYING
+--- a/COPYING
++++ b/COPYING
+@@ -# +# @@
+- Note that the only valid version of the GPL as far as this project
++ Note that the only valid version of the G.P.L as far as this project
+@@ -# +# @@
+- HOWEVER, in order to allow a migration to GPLv# if that seems like
++ HOWEVER, in order to allow a migration to G.P.Lv# if that seems like
+@@ -# +# @@
+-	This file is licensed under the GPL v#, or a later version
++	This file is licensed under the G.P.L v#, or a later version
+EOF
+
+test_expect_success \
+    'validate output from rename/copy detection' \
+    'diff -u current expected'
+
+test_done