Build an AppImage and a disk image, and publish them

Installing meant cloning the repository and running a shell script, which
is a fair ask of somebody who already has a terminal open and no ask at
all of anybody else. The releases page now carries an AppImage and a disk
image per Mac architecture: a push to master rebuilds a rolling "latest",
a v* tag publishes a version and leaves it there, and the Run button in
the Actions tab raises the number by running scripts/release.sh, which is
the same script and not a second copy of what it does.

Two things in the application had to give for that. A build has no
__main__.py on disk, and an AppImage is mounted somewhere new every run,
so the command a shortcut is registered with cannot go on being this
interpreter and this file; ipc.launcher() answers with the AppImage or
the bundle instead. And a build carries its own libstdc++, which every
process it starts inherits through LD_LIBRARY_PATH and none of them can
live with: ffmpeg, ydotool and wl-copy are the distribution's binaries
built against the distribution's libraries, and AppImageLauncher, which
is what starting the AppImage again goes through, refuses outright.
integrate.py puts that variable back before anything else runs.

Nothing installs itself over an installation that is already there.
install.sh's menu entry, install-mac.sh's login item and the desktop file
AppImageLauncher writes are each recognised and left alone, so trying a
download once does not quietly move the machine onto it. `dikte
integrate` is how you ask for it outright, and --remove takes it back.

The disk image carries an ffmpeg, pinned and checksummed, because macOS
records through one and ships nothing like it. It is signed ad-hoc and
not with an Apple certificate, so a first launch is refused until Open
Anyway and the permissions are asked for again after each update; both
READMEs and the release notes say so.

scripts/release.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# Raise the version and tag it. GitHub builds and publishes the rest.
+#
+#   ./scripts/release.sh patch      1.2.3 -> 1.2.4   a fix
+#   ./scripts/release.sh minor      1.2.3 -> 1.3.0   something new
+#   ./scripts/release.sh major      1.2.3 -> 2.0.0   something that breaks
+#   ./scripts/release.sh 2.5.0      that number, whatever is there now
+#
+# The same three words the Release button in the Actions tab offers, because
+# that button runs this script. Neither is the real one; use whichever you are
+# in front of.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+INIT="$ROOT/dikte/__init__.py"
+BUMP="${1:-}"
+YES=0
+PUSH=1
+for arg in "${@:2}"; do
+  case "$arg" in
+    --yes|-y)   YES=1 ;;
+    --no-push)  PUSH=0 ;;
+    *) echo "unknown option: $arg" >&2; exit 2 ;;
+  esac
+done
+
+die() { printf 'release: %s\n' "$1" >&2; exit 1; }
+
+CURRENT="$(sed -n 's/^__version__ = "\(.*\)"$/\1/p' "$INIT")"
+[[ -n "$CURRENT" ]] || die "no __version__ in dikte/__init__.py"
+IFS=. read -r major minor patch <<<"$CURRENT"
+
+case "$BUMP" in
+  major) NEXT="$((major + 1)).0.0" ;;
+  minor) NEXT="$major.$((minor + 1)).0" ;;
+  patch) NEXT="$major.$minor.$((patch + 1))" ;;
+  [0-9]*.[0-9]*.[0-9]*) NEXT="$BUMP" ;;
+  *) die "say major, minor, patch, or a number like 2.5.0" ;;
+esac
+TAG="v$NEXT"
+
+cd "$ROOT"
+# A release is built from what is tagged, so anything not committed would not
+# be in it, and the tag would name a tree that never existed anywhere.
+[[ -z "$(git status --porcelain)" ]] || die "commit or stash your changes first"
+git rev-parse -q --verify "refs/tags/$TAG" >/dev/null && die "$TAG already exists"
+
+if [[ $YES == 0 ]]; then
+  printf '  %s -> %s, tagged %s' "$CURRENT" "$NEXT" "$TAG"
+  [[ $PUSH == 1 ]] && printf ', and pushed to %s' "$(git rev-parse --abbrev-ref HEAD)"
+  printf '\n  Enter to go ahead, Ctrl-C to stop. '
+  read -r _
+fi
+
+# The one line, rewritten in place. A .bak and then delete it, because the BSD
+# sed on a Mac and the GNU one on Linux disagree about what -i on its own means.
+sed -i.bak "s/^__version__ = \".*\"$/__version__ = \"$NEXT\"/" "$INIT"
+rm -f "$INIT.bak"
+
+git add "$INIT"
+git commit -q -m "Dikte $NEXT"
+git tag -a "$TAG" -m "Dikte $NEXT"
+
+if [[ $PUSH == 1 ]]; then
+  git push -q origin HEAD "$TAG"
+  echo "  Pushed $TAG. Watch it build: gh run watch"
+else
+  echo "  Tagged $TAG. Push it when you are ready: git push origin HEAD $TAG"
+fi