notmuch-test: Use named-parameters for generate_message function

This makes the test suite bash-specific, but that's not much of
an issue for me, (if somebody else would prefer some other language
then they can rewrite the test suite and maintain it).

The advantage here is that we'll now be able to easily generate
custom messages for testing operations that depend on the message
content, (such as "notmuch reply", etc.).

test/notmuch-test

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 set -e
 
 find_notmuch_binary ()
@@ -25,17 +25,29 @@ find_notmuch_binary ()
 #
 # The filename of the message generated is available as
 # $gen_msg_filename
+#
+# This function supports named parameters with the bash syntax for
+# assigning a value to an associative array ([name]=value). The
+# supported parameters are:
+#
+#  [dir]=directory/of/choice
+#
+#	Generate the message in directory 'directory/of/choice' within
+#	the mail store. The directory will be created if necessary.
 gen_msg_cnt=0
 gen_msg_filename=""
 generate_message ()
 {
+    # This is our (bash-specific) magic for doing named parameters
+    local -A template="($@)"
+
     gen_msg_cnt=$((gen_msg_cnt + 1))
     gen_msg_name=msg-$(printf "%03d" $gen_msg_cnt)
 
-    if [ "$#" = "0" ]; then
+    if [ -z "${template[dir]}" ]; then
 	gen_msg_filename="${MAIL_DIR}/$gen_msg_name"
     else
-	gen_msg_filename="${MAIL_DIR}/$1/$gen_msg_name"
+	gen_msg_filename="${MAIL_DIR}/${template[dir]}/$gen_msg_name"
 	mkdir -p $(dirname $gen_msg_filename)
     fi
 
@@ -114,7 +126,7 @@ printf " New directories...\t\t"
 rm -rf ${MAIL_DIR}/* ${MAIL_DIR}/.notmuch
 mkdir ${MAIL_DIR}/def
 mkdir ${MAIL_DIR}/ghi
-generate_message def
+generate_message [dir]=def
 
 execute_expecting new "Added 1 new message to the database."
 
@@ -123,7 +135,7 @@ printf " Alternate inode order...\t"
 rm -rf ${MAIL_DIR}/.notmuch
 mv ${MAIL_DIR}/ghi ${MAIL_DIR}/abc
 rm ${MAIL_DIR}/def/*
-generate_message abc
+generate_message [dir]=abc
 
 execute_expecting new "Added 1 new message to the database."
 
@@ -157,9 +169,9 @@ execute_expecting new "No new mail. Removed 1 message."
 printf " Renamed directory...\t\t"
 
 do_sleep
-generate_message dir
+generate_message [dir]=dir
-generate_message dir
+generate_message [dir]=dir
-generate_message dir
+generate_message [dir]=dir
 
 $NOTMUCH new > /dev/null
 
@@ -178,9 +190,9 @@ execute_expecting new "No new mail. Removed 3 messages."
 printf " New directory (at end of list)... "
 
 do_sleep
-generate_message zzz
+generate_message [dir]=zzz
-generate_message zzz
+generate_message [dir]=zzz
-generate_message zzz
+generate_message [dir]=zzz
 
 execute_expecting new "Added 3 new messages to the database."
 
@@ -214,9 +226,9 @@ execute_expecting new "Added 1 new message to the database."
 printf " New two-level directory...\t"
 
 do_sleep
-generate_message two/levels
+generate_message [dir]=two/levels
-generate_message two/levels
+generate_message [dir]=two/levels
-generate_message two/levels
+generate_message [dir]=two/levels
 
 execute_expecting new "Added 3 new messages to the database."