feat(sterni/acme): add initial plumbing rules

Rules for the Plan 9 plumber (see https://9p.io/sys/doc/plumb.pdf)
allowing quick navigation through depot (and related services) in acme.

- man, urls: some rules that I like taken from /plumb/basic and split
  across individual files.
- tvl: incomplete support for TVL short links and targets:
  - //…
  - cl/…
  - b/…

As mentioned, these are incomplete and I want to implement the remaining
short links and things like git support. I want to continue
experimenting with the plumber, but what I've got so far is already
pretty cool. Eventually, I'll want to implement something equivalent for
Emacs (maybe via Hyperbole) which is probably going to be of general
interest to depot users.

Change-Id: I678f000369db4c7ce30b2aedbc2dbccf3ddef0a9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13026
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Autosubmit: sterni <sternenseemann@systemli.org>

users/sterni/acme/plumb/default.nix

@@ -0,0 +1,39 @@
+{ pkgs, lib, ... }:
+
+pkgs.stdenvNoCC.mkDerivation {
+  name = "sterni-plumb";
+
+  src = builtins.path {
+    path = ./.;
+    filter = path: _: !(lib.hasSuffix "default.nix" path);
+  };
+
+  dontConfigure = true;
+  dontBuild = true;
+
+  # The write will fail if there's something wrong with the rules,
+  # though it only detects some problems.
+  checkPhase = ''
+    runHook preInstall
+    export NAMESPACE="$(mktemp -d)"
+    9 plumber -f &
+    pid="$!"
+    until [[ -e "$NAMESPACE/plumb" ]]; do
+      sleep 0.1
+    done
+    9 9p write plumb/rules < sterni.plumbing
+    kill "$pid"
+    runHook postInstall
+  '';
+  doCheck = true;
+  checkInputs = [
+    pkgs.plan9port
+  ];
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p "$out"
+    mv * "$out/"
+    runHook postInstall
+  '';
+}

users/sterni/acme/plumb/man

@@ -0,0 +1,4 @@
+# Man pages (taken from /plumb/basic), e.g. man(1)
+type is text
+data matches '([a-zA-Z¡-0-9_\-./]+)\(([1-8])\)'
+plumb start rc -c 'man '$2' '$1' >[2=1] | nobs | plumb -i -d edit -a ''action=showdata filename=/man/'$1'('$2')'''

users/sterni/acme/plumb/sterni.plumbing

@@ -0,0 +1,12 @@
+# TODO(sterni): are rules for :linenumber etc. needed or acme default?
+# TODO(sterni): file: urls
+# TODO(sterni): xdg-open for mail addresses, images, pdfs etc.
+# TODO(sterni): git
+
+editor = acme
+include man
+
+depot = /home/lukas/src/depot
+include tvl
+
+include urls

users/sterni/acme/plumb/tvl

@@ -0,0 +1,71 @@
+# TODO(sterni): document TVL short links,
+# for now see //tools/cheddar, //web/atward, //tools/magrathea
+# and //ops/modules/monorepo-gerrit.
+# TODO(sterni): r/([0-9]+)
+
+# TVL short links that go to the browser, e.g. cl/8413, b/187
+
+type is text
+data matches 'cl/([0-9]+)'
+data set https://cl.tvl.fyi/c/depot/+/$1
+plumb to web
+plumb start web $data
+
+type is text
+data matches 'b/([0-9]+)'
+data set https://b.tvl.fyi/issues/$1
+plumb to web
+plumb start web $data
+
+# TVL target short links
+
+# TODO(sterni): implement subtargets
+# TODO(sterni): can we add an acme address to target paths somehow?
+
+# TODO(sterni): look at //tools/magrathea's parsing.
+depotpathchar = '[^:.,!"'' ]'
+depotpath = '//('$depotpathchar'+)'
+
+# TVL short links to files in depot, open in local editor, e.g.
+#
+# - //users/sterni/acme/plumb/tvl,
+# - //default.nix,
+# - //nix/readTree/README.md,
+# - //tools/magrathea/mg.scm
+#
+# We impose the same restrictions for the initial path,
+# but are liberal in the file name
+
+type is text
+data matches '//('$depotchar'+/)?([^ ]*'$depotpathchar')'
+arg isfile $depot/$1$2
+data set $file
+plumb to edit
+plumb client $editor
+
+# TVL short links to directories in depot, mapped to default.nix, e.g. //nix/readTree
+
+type is text
+data matches $depotpath
+arg isfile $depot/$1/default.nix
+data set $file
+plumb to edit
+plumb client $editor
+
+# TVL short links to targets that aren't expressed by default.nix, e.g. //third_party/lisp/alexandria
+
+type is text
+data matches $depotpath
+arg isfile $depot/$1.nix
+data set $file
+plumb to edit
+plumb client $editor
+
+# TVL short links to directories in depot (without default.nix), e.g. //ops/machines
+
+type is text
+data matches $depotpath
+arg isdir $depot/$1
+data set $dir
+plumb to edit
+plumb client $editor

users/sterni/acme/plumb/urls

@@ -0,0 +1,7 @@
+# URLs, e.g. https://tvl.fyi
+# Based on /plumb/basic, but with most protocols removed
+# TODO(sterni): add default case to xdg-open
+type	is	text
+data	matches	'(https?)://[a-zA-Z0-9_@\-]+([.:][a-zA-Z0-9_@\-]+)*/?[a-zA-Z0-9_?,%#~&/\-+=]+([:.][a-zA-Z0-9_?,%#~&/\-+=]+)*'
+plumb	to	web
+plumb	start	web $0