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The canonical .dockerignore was three lines -- .git, node_modules, .DS_Store -- while the canonical Dockerfile does `COPY . .`, so a developer's local .env, *.pem or *.key was shipped into the build context and could land in an image layer. Nothing surfaced it because .gitignore covers those patterns, so the files are invisible to every git-based check. The obvious repair, copying .gitignore's secret patterns across, is worse than the gap it closes. .dockerignore does not use .gitignore semantics: Docker matches with Go filepath.Match, `*` does not cross `/`, and a pattern without a leading `**/` is anchored at the build-context root. A file listing .env, *.pem and *.key therefore reads as solved, reviews as solved, and protects only the repository root, while config/.env and certs/server.key still ship. The three-line file at least invited scrutiny; the transplanted form manufactures confidence and stops anyone looking. So every depth-independent pattern here carries the `**/` prefix and only genuinely root-anchored entries stay unprefixed. `**/node_modules` fixes a defect the three-line file had today for any nested node_modules, independently of the secret exposure. The OS and editor patterns are included on their own merits rather than by mirroring .gitignore. None of them is ever a build input, and editor state in particular churns under a developer's hands, so each one is a source of `COPY . .` invalidation carrying no information about the source tree. Now that the checks are keyed on CHECK_EPOCH rather than on accidental context churn, there is no reason left to keep churn in the context. Language build artifacts are deliberately absent: they are per-repo, and the file's header comment tells consuming repos to add their own host-built binaries, which is the case that actually bites -- a host `make build` drops a multi-megabyte artifact into the context where .gitignore hides it from every git-based check. .gitignore is untouched. Its semantics are the inverse: an unanchored pattern already matches at any depth, so `**/`-prefixing it produces a file that is wrong in a way that looks careful. That asymmetry is why "derive one from the other" was the wrong instruction, and it is now written down in REPO_POLICIES.md in both directions, together with the requirement to verify by enumerating the image rather than by reading the patterns. Every consuming repo inherits .dockerignore by copy, so the trap has to live where the next person looks, not only be fixed once here. Both repo checklists gain the same requirement, since they are what an agent reads while extending the file. Verified by planting .env, server.key and ca.pem at the root plus config/.env, config/.env.production, certs/ca.pem, certs/server.key, deploy/secrets/id_rsa.key, web/node_modules/nested/index.js and a nested .swp below it, then building a standalone probe image doing `COPY . .` and listing what actually landed inside it. Before: all eleven planted files in the image. Against the naive unprefixed form: the three root-level files excluded and every nested one still present, which is what shows the enumeration can detect the failure mode at all. After: every planted file excluded at every depth, with web/src/app.js still present to prove the probe was copying nested files rather than copying nothing. Transferred-context size is recorded but load-bearing on nothing, and the runs show why: the naive build reported 2.18kB transferred while 43 files, five of them secrets, were in the image. BuildKit transfers only the delta from the previous build, so the number describes the transfer and not the contents. Planted files were removed and their absence confirmed against the filesystem rather than against `git status`, which could not have seen them. `make docker` re-run after the change: the check layer executed rather than being served from cache, so the CHECK_EPOCH verification still holds under the altered build context.
37 lines
1.1 KiB
Plaintext
37 lines
1.1 KiB
Plaintext
# .dockerignore uses Go filepath.Match, NOT .gitignore semantics: `*`
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# does not cross `/`, and a pattern without a leading `**/` is anchored
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# at the build-context root. Every depth-independent pattern therefore
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# needs the `**/` prefix — without it `config/.env` and
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# `certs/server.key` still ship while the file reads as solved. Entries
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# that are genuinely root-anchored stay unprefixed. Extend this file
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# with the repo's own host-built artifacts (compiled binaries, test
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# binaries, coverage output); those are per-repo and belong here because
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# a host build otherwise drops them into the context.
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# Repository metadata: exactly one, at the context root.
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.git
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# Environment and secrets. These are the reason the prefixes matter: a
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# developer's local copy is invisible to every git-based check.
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**/.env
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**/.env.*
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**/*.pem
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**/*.key
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# Dependencies: restored inside the image, never copied in.
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**/node_modules
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# OS metadata.
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**/.DS_Store
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**/Thumbs.db
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# Editor state. Never a build input, and it churns under a developer's
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# hands, so it invalidates COPY for reasons unrelated to the source.
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**/*.swp
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**/*.swo
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**/*~
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**/*.bak
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**/.idea
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**/.vscode
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**/*.sublime-*
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