Fix overwriting of files when applying contextually independent diffs

Noticed by applying two diffs of different contexts to the same file.

The check for existence of a file was wrong: the test assumed it was
a directory and reset the errno (twice: directly and by calling
lstat). So if an entry existed and was _not_ a directory no attempt
was made to rename into it, because the errno (expected by renaming
code) was already reset to 0. This resulted in error:

    fatal: unable to write file file mode 100644

For Linux, removing "errno = 0" is enough, as lstat wont modify errno
if it was successful. The behavior should not be depended upon,
though, so modify the "if" as well.

The test simulates this situation.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/builtin-apply.c b/builtin-apply.c
index a5d612655f82e071c8e7d961660a6f1d562f6f40..db5272245569f4080a07cdb3a2aacd2c0cbda38c 100644 (file)
--- a/builtin-apply.c
+++ b/builtin-apply.c
@@ -2416,8 +2416,7 @@ static void create_one_file(char *path, unsigned mode, const char *buf, unsigned
                 * used to be.
                 */
                struct stat st;
-               errno = 0;
-               if (!lstat(path, &st) && S_ISDIR(st.st_mode) && !rmdir(path))
+               if (!lstat(path, &st) && (!S_ISDIR(st.st_mode) || !rmdir(path)))
                        errno = EEXIST;
        }
 

diff --git a/t/t4121-apply-diffs.sh b/t/t4121-apply-diffs.sh
new file mode 100755 (executable)
index 0000000..2b2f1ed
--- /dev/null
+++ b/t/t4121-apply-diffs.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+
+test_description='git-apply for contextually independent diffs'
+. ./test-lib.sh
+
+echo '1
+2
+3
+4
+5
+6
+7
+8' >file
+
+test_expect_success 'setup' \
+       'git add file &&
+       git commit -q -m 1 &&
+       git checkout -b test &&
+       mv file file.tmp &&
+       echo 0 >file &&
+       cat file.tmp >>file &&
+       rm file.tmp &&
+       git commit -a -q -m 2 &&
+       echo 9 >>file &&
+       git commit -a -q -m 3 &&
+       git checkout master'
+
+test_expect_success \
+       'check if contextually independent diffs for the same file apply' \
+       '( git diff test~2 test~1; git diff test~1 test~0 )| git apply'
+
+test_done
+