test: Use skipTest instead of exit 0

This way shellcheck is ok with it, and it conveys that a significant
chunk of the test is skipped.

(cherry picked from commit 414c346)

# Conflicts:
#	tests/functional/help.sh

tests/functional/help.sh

@@ -2,6 +2,34 @@
 
 source common.sh
 
+<<<<<<< HEAD
+=======
+function subcommands() {
+  jq -r '
+def recurse($prefix):
+    to_entries[] |
+    ($prefix + [.key]) as $newPrefix |
+    (if .value | has("commands") then
+      ($newPrefix, (.value.commands | recurse($newPrefix)))
+    else
+      $newPrefix
+    end);
+.args.commands | recurse([]) | join(" ")
+'
+}
+
+nix __dump-cli | subcommands | while IFS= read -r cmd; do
+    # shellcheck disable=SC2086 # word splitting of cmd is intended
+    nix $cmd --help
+done
+
+[[ $(type -p man) ]] || skipTest "'man' not installed"
+
+# FIXME: we don't know whether we built the manpages, so we can't
+# reliably test them here.
+skipTest "we don't know whether we built the manpages, so we can't reliably test them here."
+
+>>>>>>> 414c34656 (test: Use skipTest instead of exit 0)
 # test help output
 
 nix-build --help
@@ -49,6 +77,7 @@ nix-daemon --help
 nix-hash --help
 nix-instantiate --help
 nix-prefetch-url --help
+<<<<<<< HEAD
 
 function subcommands() {
   jq -r '
@@ -68,3 +97,5 @@ nix __dump-cli | subcommands | while IFS= read -r cmd; do
     # shellcheck disable=SC2086 # word splitting of cmd is intended
     nix $cmd --help
 done
+=======
+>>>>>>> 414c34656 (test: Use skipTest instead of exit 0)