filter-branch: add a test for the commit removal example

In the man page, there is an example which describes how to remove
single commits (although it keeps the changes which were not reverted
in the next non-removed commit). Better make sure that it works as
expected.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7003-filter-branch.sh

@@ -107,4 +107,39 @@ test_expect_success 'use index-filter to move into a subdirectory' '
 		  mv \$GIT_INDEX_FILE.new \$GIT_INDEX_FILE" directorymoved &&
 	test -z "$(git diff HEAD directorymoved:newsubdir)"'
 
+test_expect_success 'author information is preserved' '
+	: > i &&
+	git add i &&
+	test_tick &&
+	GIT_AUTHOR_NAME="B V Uips" git commit -m bvuips &&
+	git-filter-branch --msg-filter "cat; \
+			test \$GIT_COMMIT = $(git rev-parse master) && \
+			echo Hallo" \
+		preserved-author &&
+	test 1 = $(git rev-list --author="B V Uips" preserved-author | wc -l)
+'
+
+test_expect_success "remove a certain author's commits" '
+	echo i > i &&
+	test_tick &&
+	git commit -m i i &&
+	git-filter-branch --commit-filter "\
+		if [ \"\$GIT_AUTHOR_NAME\" = \"B V Uips\" ];\
+		then\
+			shift;\
+			while [ -n \"\$1\" ];\
+			do\
+				shift;\
+				echo \"\$1\";\
+				shift;\
+			done;\
+		else\
+			git commit-tree \"\$@\";\
+		fi" removed-author &&
+	cnt1=$(git rev-list master | wc -l) &&
+	cnt2=$(git rev-list removed-author | wc -l) &&
+	test $cnt1 -eq $(($cnt2 + 1)) &&
+	test 0 = $(git rev-list --author="B V Uips" removed-author | wc -l)
+'
+
 test_done