let a stack compute its settings without make

A stack can now ship <name>.env and <name>.sh next to its compose files. The
hook is sourced with the tag helpers available, which is what the computing
.mk files of the catalogue were using make for: 29 of its 44 .mk files only
exist to build variables like the fabio tags.

Converting stack/host/fabio.mk by hand gives byte-identical output for the
route tag, and drops a trailing comma the make version left in the listener
list.

Also: APP_HOST and APP_URI are computed (the tag helpers build on them),
--color controls the escape codes rather than always emitting them, and
make test-portability runs the CLI under busybox ash and dash.

lib/hooks.sh

@@ -0,0 +1,28 @@
+#shellcheck shell=sh
+# hooks: the per-stack settings that used to live in a .mk file.
+#
+# A stack may ship, next to its compose files:
+#   <name>.env       dotenv, for plain values
+#   <name>.env.<env> the same, for one environment
+#   <name>.sh        shell, for values that have to be computed (fabio tags, JWTs)
+#   <name>.mk        the legacy make snippet, still read for its groups
+#
+# A .sh hook runs with the myos helpers available (myos_tagprefix, myos_uri,
+# myos_var) and sets variables directly. This is what lets a stack of the
+# catalogue work on a machine that has no make.
+
+# myos_stack_hooks DIR NAME  load the hooks of one stack, most specific last
+myos_stack_hooks() {
+  _hdir=$1; _hname=$2
+  for _h in "$_hdir/$_hname.env" "$_hdir/$_hname.env.$ENV"; do
+    [ -f "$_h" ] && myos_dotenv_load "$_h"
+  done
+  for _h in "$_hdir/$_hname.sh" "$_hdir/$_hname.$ENV.sh"; do
+    if [ -f "$_h" ]; then
+      myos_debug "hook $_h"
+      # shellcheck source=/dev/null
+      . "$_h"
+    fi
+  done
+  return 0
+}