test: make it possible to have multiple corpora

We largely use the corpus under test/corpus for
testing. Unfortunately, many of our tests have grown to depend on
having exactly this set of messages, making it hard to add new message
files for testing specific cases.

We do use a lot of add_message from within the tests, but it's not
possible to use that for adding broken messages, and adding several
messages at once can get unwieldy.

Move the basic corpus under tests/corpora/default, and make it
possible to add new, independent corpora along its side. This means
tons of renames with a few tweaks to add_email_corpus function in
test-lib.sh to let tests specify which corpus to use.

test/test-lib.sh

@@ -541,21 +541,26 @@ emacs_fcc_message ()
     notmuch new >/dev/null
 }
 
-# Generate a corpus of email and add it to the database.
+# Add an existing, fixed corpus of email to the database.
 #
-# This corpus is fixed, (it happens to be 50 messages from early in
-# the history of the notmuch mailing list), which allows for reliably
+# $1 is the corpus dir under corpora to add, using "default" if unset.
+#
+# The default corpus is based on about 50 messages from early in the
+# history of the notmuch mailing list, which allows for reliably
 # testing commands that need to operate on a not-totally-trivial
 # number of messages.
 add_email_corpus ()
 {
+    corpus=${1:-default}
+
     rm -rf ${MAIL_DIR}
-    if [ -d $TEST_DIRECTORY/corpus.mail ]; then
-	cp -a $TEST_DIRECTORY/corpus.mail ${MAIL_DIR}
+    if [ -d $TEST_DIRECTORY/corpora.mail/$corpus ]; then
+	cp -a $TEST_DIRECTORY/corpora.mail/$corpus ${MAIL_DIR}
     else
-	cp -a $TEST_DIRECTORY/corpus ${MAIL_DIR}
+	cp -a $TEST_DIRECTORY/corpora/$corpus ${MAIL_DIR}
 	notmuch new >/dev/null || die "'notmuch new' failed while adding email corpus"
-	cp -a ${MAIL_DIR} $TEST_DIRECTORY/corpus.mail
+	mkdir -p $TEST_DIRECTORY/corpora.mail
+	cp -a ${MAIL_DIR} $TEST_DIRECTORY/corpora.mail/$corpus
     fi
 }