Add --no-activate flag

The trick is in getting Liquidprompt to be testable. My first attempt
kinda works, but more is needed. Liquidprompt has a lot of hacks to
check if the environment it is launched in is actually a valid
interactive shell, and bail if not. The issue is that a test environment
isn't an interactive shell, but we still need Liquidprompt to load all
its functions so we can test them.

The removal of the '$PS1' check in Bash is simply because it isn't a
good test for an interactive Bash shell. PS1 could be unset by a user,
and it could be set (pointlessly) by a script. The [[ "$-" == *i* ]]
test is much better. We tell users to use that in the docs, but it might
be a good idea to add it to our auto-starting check.

This flag when set will skip the hooking in of Liquidprompt to the
shell, so that functions will be loaded into the environment, but not
run.

liquidprompt

@@ -24,7 +24,7 @@
 test -z "$TERM" -o "x$TERM" = xdumb && return
 
 # Check for recent enough version of bash.
-if test -n "${BASH_VERSION-}" -a -n "$PS1" ; then
+if test -n "${BASH_VERSION-}"; then
     if (( ${BASH_VERSINFO[0]:-0} < 3 || ( ${BASH_VERSINFO[0]:-0} == 3 && ${BASH_VERSINFO[1]:-0} < 2 ) )); then
         echo "liquidprompt: Bash version $BASH_VERSION not supported" 2>&1
         return
@@ -1967,6 +1967,8 @@ prompt_OFF()
 }
 
 # By default, sourcing liquidprompt will activate Liquid Prompt
-prompt_on
+if [ "${1-}" != "--no-activate" ]; then
+    prompt_on
+fi
 
 # vim: set et sts=4 sw=4 tw=120 ft=sh:

tests/test_shell.sh

@@ -214,7 +214,7 @@ function test_parameter_expansion_replace {
   assertEquals "Parameter expansion replace start" cdabcd "${var/#ab}"
   assertEquals "Parameter expansion replace start no match" $var "${var/#b}"
 
-  assertEquals "Parame'ter expansion replace end" abcdab "${var/%cd}"
+  assertEquals "Parameter expansion replace end" abcdab "${var/%cd}"
   assertEquals "Parameter expansion replace end no match" $var "${var/%c}"
 }