test-lib-functions: add helper for trailing hash

It can be helpful to check that a file format with a trailing hash has a
specific hash in the final bytes of a written file. This is made more
apparent by recent changes that allow skipping the hash algorithm and
writing a null hash at the end of the file instead.

Add a new test_trailing_hash helper and use it in t1600 to verify that
index.skipHash=true really does skip the hash computation, since
'git fsck' does not actually verify the hash. This confirms that when
the config is disabled explicitly in a super project but enabled in a
submodule, then the use of repo_config_get_bool() loads config from the
correct repository in the case of 'git add'. There are other cases where
istate->repo is NULL and thus this config is loaded instead from
the_repository, but that's due to many different code paths initializing
index_state structs in their own way.

Keep the 'git fsck' call to ensure that any potential future change to
check the index hash does not cause an error in this case.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t1600-index.sh b/t/t1600-index.sh
index 98c5a83db73a34bd1828e7895032e97be727953f..2f792bb8ffa491759f83979df4d68086fc710235 100755 (executable)
--- a/t/t1600-index.sh
+++ b/t/t1600-index.sh
@@ -68,6 +68,9 @@ test_expect_success 'out of bounds index.version issues warning' '
 test_expect_success 'index.skipHash config option' '
        rm -f .git/index &&
        git -c index.skipHash=true add a &&
+       test_trailing_hash .git/index >hash &&
+       echo $(test_oid zero) >expect &&
+       test_cmp expect hash &&
        git fsck &&
 
        test_commit start &&
@@ -76,6 +79,8 @@ test_expect_success 'index.skipHash config option' '
        git -C sub config index.skipHash true &&
        >sub/file &&
        git -C sub add a &&
+       test_trailing_hash .git/modules/sub/index >hash &&
+       test_cmp expect hash &&
        git -C sub fsck
 '
 

diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 796093a7b32f983a558d8ef6ea2f406c8edd70da..60308843f8f4f0063dd5958004c3146e0993ac08 100644 (file)
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1875,3 +1875,11 @@ test_cmp_config_output () {
        sort config-actual >sorted-actual &&
        test_cmp sorted-expect sorted-actual
 }
+
+# Given a filename, extract its trailing hash as a hex string
+test_trailing_hash () {
+       local file="$1" &&
+       tail -c $(test_oid rawsz) "$file" |
+               test-tool hexdump |
+               sed "s/ //g"
+}