build: let a packaged build say which build it is (opt-in APP_BUILD)

[kurktchiev]

__APP_VERSION__ is read from frontend/package.json, so every image built between two releases reports the same number. From inside the app there is no way to tell one build of 1.3.7 from another — which means the question a bug report turns on, which build were you running?, has no answer, and "I tested it, no change" cannot be told apart from a stale service-worker cache.

That happened to me twice in one day on a self-hosted deployment: two rounds of testing a timer change were unresolvable because the tester's phone reported v1.3.7 either way.

The change

Two lines of substance:

• frontend/vite.config.js — when process.env.APP_BUILD is set, __APP_VERSION__ becomes `${pkgVersion}+${APP_BUILD}`. Unset, it is exactly pkgVersion, as now.
• web/Dockerfile — takes ARG APP_BUILD="" in the build stage and passes it to npm run build. (The existing VERSION/VCS_REF args live in the runtime stage, which is after vite has already run, so they cannot reach the bundle.)

Nothing else moves. Settings → About and the footer already render __APP_VERSION__, so a build that sets it reads openGym v1.3.7+2026-09-17.3 and one that does not reads openGym v1.3.7.

Why opt-in rather than always-on

A release build should say 1.3.7 and nothing else — that is the number people are asked for, and 1.3.7+abc1234 in a release would be noise. The suffix is for builds that are not releases: CI artifacts, nightlies, a self-hoster's own image. docker compose up --build without the arg is unchanged, which is the path almost every self-hoster takes.

Suggested use in CI: --build-arg APP_BUILD=$CI_PIPELINE_ID or a date stamp.

Checked

• npm test in frontend/ — 1468 passing across 100 files
• npm run build with APP_BUILD=demo.1 → the bundle contains 1.3.7+demo.1
• npm run build with it unset → the bundle contains no + suffix at all, i.e. the string is byte-identical to today's
• No new dependency; process.env is already how vite config reads its environment
• CHANGELOG.md left alone

🤖 Generated with Claude Code

[DuarteSantos8]

Thanks @kurktchiev. With APP_BUILD set, Settings shows v1.3.9+<build> and the update check ignores the build part on both sides (the version-compare fix from #250 went in first). Nothing in CI sets it yet, so it stays opt-in.

Released in v1.3.9: https://github.com/DuarteSantos8/openGym/releases/tag/v1.3.9