apply --reverse: tie it all together.

Add a few tests, usage string, and documentation.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-apply.txt

@@ -10,7 +10,8 @@ SYNOPSIS
 --------
 [verse]
 'git-apply' [--stat] [--numstat] [--summary] [--check] [--index] [--apply]
-	  [--no-add] [--index-info] [--allow-binary-replacement] [-z] [-pNUM]
+	  [--no-add] [--index-info] [--allow-binary-replacement]
+	  [--reverse] [-z] [-pNUM]
 	  [-CNUM] [--whitespace=<nowarn|warn|error|error-all|strip>]
 	  [<patch>...]
 
@@ -62,6 +63,9 @@ OPTIONS
 	the original version of the blob is available locally,
 	outputs information about them to the standard output.
 
+--reverse::
+	Apply the patch in reverse.
+
 -z::
 	When showing the index information, do not munge paths,
 	but use NUL terminated machine readable format.  Without

builtin-apply.c

@@ -43,7 +43,7 @@ static int show_index_info;
 static int line_termination = '\n';
 static unsigned long p_context = -1;
 static const char apply_usage[] =
-"git-apply [--stat] [--numstat] [--summary] [--check] [--index] [--cached] [--apply] [--no-add] [--index-info] [--allow-binary-replacement] [-z] [-pNUM] [-CNUM] [--whitespace=<nowarn|warn|error|error-all|strip>] <patch>...";
+"git-apply [--stat] [--numstat] [--summary] [--check] [--index] [--cached] [--apply] [--no-add] [--index-info] [--allow-binary-replacement] [--reverse] [-z] [-pNUM] [-CNUM] [--whitespace=<nowarn|warn|error|error-all|strip>] <patch>...";
 
 static enum whitespace_eol {
 	nowarn_whitespace,

t/t4116-apply-reverse.sh

@@ -22,25 +22,64 @@ test_expect_success setup '
 	tr "[mon]" '\''[\0\1\2]'\'' <file1 >file2 &&
 
 	git commit -a -m second &&
+	git tag second &&
 
-	git diff --binary -R initial >patch
+	git diff --binary initial second >patch
 
 '
 
 test_expect_success 'apply in forward' '
 
+	T0=`git rev-parse "second^{tree}"` &&
+	git reset --hard initial &&
 	git apply --index --binary patch &&
-	git diff initial >diff &&
-	diff -u /dev/null diff
-
+	T1=`git write-tree` &&
+	test "$T0" = "$T1"
 '
 
 test_expect_success 'apply in reverse' '
 
+	git reset --hard second &&
 	git apply --reverse --binary --index patch &&
 	git diff >diff &&
 	diff -u /dev/null diff
 
 '
 
+test_expect_success 'setup separate repository lacking postimage' '
+
+	git tar-tree initial initial | tar xf - &&
+	(
+		cd initial && git init-db && git add .
+	) &&
+
+	git tar-tree second second | tar xf - &&
+	(
+		cd second && git init-db && git add .
+	)
+
+'
+
+test_expect_success 'apply in forward without postimage' '
+
+	T0=`git rev-parse "second^{tree}"` &&
+	(
+		cd initial &&
+		git apply --index --binary ../patch &&
+		T1=`git write-tree` &&
+		test "$T0" = "$T1"
+	)
+'
+
+test_expect_success 'apply in reverse without postimage' '
+
+	T0=`git rev-parse "initial^{tree}"` &&
+	(
+		cd second &&
+		git apply --index --binary --reverse ../patch &&
+		T1=`git write-tree` &&
+		test "$T0" = "$T1"
+	)
+'
+
 test_done