fsck: test and document unknown fsck.<msg-id> values

When fsck.<msg-id> is set to an unknown value it'll cause "fsck" to
die, but the same is not true of the "fetch" and "receive"
variants. Document this and test for it.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1637,6 +1637,10 @@ In general, it is better to enumerate existing objects with problems
 with `fsck.skipList`, instead of listing the kind of breakages these
 problematic objects share to be ignored, as doing the latter will
 allow new instances of the same breakages go unnoticed.
++
+Setting an unknown `fsck.<msg-id>` value will cause fsck to die, but
+doing the same for `receive.fsck.<msg-id>` and `fetch.fsck.<msg-id>`
+will only cause git to warn.
 
 fsck.skipList::
 	The path to a sorted list of object names (i.e. one SHA-1 per

t/t5504-fetch-receive-strict.sh

@@ -198,6 +198,10 @@ test_expect_success 'fetch with fetch.fsck.skipList' '
 	git --git-dir=dst/.git fetch "file://$(pwd)" $refspec
 '
 
+test_expect_success 'fsck.<unknownmsg-id> dies' '
+	test_must_fail git -c fsck.whatEver=ignore fsck 2>err &&
+	test_i18ngrep "Unhandled message id: whatever" err
+'
 
 test_expect_success 'push with receive.fsck.missingEmail=warn' '
 	commit="$(git hash-object -t commit -w --stdin <bogus-commit)" &&
@@ -211,10 +215,15 @@ test_expect_success 'push with receive.fsck.missingEmail=warn' '
 	git --git-dir=dst/.git config fsck.missingEmail warn &&
 	test_must_fail git push --porcelain dst bogus &&
 
+	# receive.fsck.<unknownmsg-id> warns
+	git --git-dir=dst/.git config \
+		receive.fsck.whatEver error &&
+
 	git --git-dir=dst/.git config \
 		receive.fsck.missingEmail warn &&
 	git push --porcelain dst bogus >act 2>&1 &&
 	grep "missingEmail" act &&
+	test_i18ngrep "Skipping unknown msg id.*whatever" act &&
 	git --git-dir=dst/.git branch -D bogus &&
 	git --git-dir=dst/.git config --add \
 		receive.fsck.missingEmail ignore &&
@@ -235,10 +244,15 @@ test_expect_success 'fetch with fetch.fsck.missingEmail=warn' '
 	git --git-dir=dst/.git config fsck.missingEmail warn &&
 	test_must_fail git --git-dir=dst/.git fetch "file://$(pwd)" $refspec &&
 
+	# receive.fsck.<unknownmsg-id> warns
+	git --git-dir=dst/.git config \
+		fetch.fsck.whatEver error &&
+
 	git --git-dir=dst/.git config \
 		fetch.fsck.missingEmail warn &&
 	git --git-dir=dst/.git fetch "file://$(pwd)" $refspec >act 2>&1 &&
 	grep "missingEmail" act &&
+	test_i18ngrep "Skipping unknown msg id.*whatever" act &&
 	rm -rf dst &&
 	git init dst &&
 	git --git-dir=dst/.git config fetch.fsckobjects true &&