chore(dev): add Dockerfile.jailoc for in-container development (#77)

* chore(gitignore): add .envrc

* chore(dev): add Dockerfile.jailoc for in-container development

* dev(dockerfile): keep 1.26.1

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* chore(dev): move Dockerfile.jailoc to dev/ and fix docs

---------

Co-authored-by: Speedo17 <jan.trnka@firma.seznam.cz>
Co-authored-by: Josef Kolář <thejoeejoee@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 4 people

AGENTS.md

@@ -88,6 +88,23 @@ Two services per workspace on a shared Docker network:
 - `t.Setenv()` is incompatible with `t.Parallel()` — tests using `t.Setenv` must NOT be parallel
 - `httptest.NewServer` in parallel subtests: use `t.Cleanup(ts.Close)`, NOT `defer ts.Close()` (defer runs before parallel subtests start)
 
+## Development environment
+
+`dev/Dockerfile.jailoc` is a workspace overlay for developing jailoc
+inside a jailoc container. It extends the base image with the Go toolchain, gopls,
+and golangci-lint matching CI.
+
+Add to `~/.config/jailoc/config.toml`:
+
+```toml
+[workspaces.jailoc]
+paths = ["/path/to/jailoc"]
+dockerfile = "https://raw.githubusercontent.com/seznam/jailoc/main/dev/Dockerfile.jailoc"
+```
+
+`jailoc up jailoc` starts a container with Go, gopls, and golangci-lint on PATH.
+Run `go build`, `go test ./...`, and `golangci-lint run` inside as usual.
+
 ## CI/CD
 
 GitHub Actions workflows:

dev/Dockerfile.jailoc

@@ -0,0 +1,36 @@
+# Workspace overlay image for developing jailoc inside a jailoc container.
+# Extends the jailoc base image with the Go toolchain, gopls, and golangci-lint.
+#
+# Usage — add to ~/.config/jailoc/config.toml:
+#
+#   [workspaces.jailoc]
+#   paths = ["/path/to/jailoc"]
+#   dockerfile = "https://raw.githubusercontent.com/seznam/jailoc/main/dev/Dockerfile.jailoc"
+#
+# jailoc injects the resolved base image via the BASE build arg.
+
+ARG BASE
+FROM ${BASE}
+
+# Go toolchain — required by golangci-lint and gopls at runtime.
+# renovate: datasource=golang-version depName=go
+ARG GO_VERSION=1.26.1
+RUN set -eux; \
+    ARCH=$(dpkg --print-architecture); \
+    curl -fsSL "https://go.dev/dl/go${GO_VERSION}.linux-${ARCH}.tar.gz" \
+    | tar -xzC /usr/local
+ENV PATH="/usr/local/go/bin:${PATH}"
+
+# gopls — Go language server for OpenCode code intelligence (go-to-definition, completions, diagnostics).
+# renovate: datasource=go depName=golang.org/x/tools/gopls
+ARG GOPLS_VERSION=v0.21.1
+RUN GOBIN=/usr/local/bin go install golang.org/x/tools/gopls@${GOPLS_VERSION}
+
+# golangci-lint — static analysis matching CI (gosec, staticcheck, gocritic).
+# renovate: datasource=github-releases depName=golangci/golangci-lint
+ARG GOLANGCI_LINT_VERSION=v2.10.1
+RUN set -eux; \
+    ARCH=$(dpkg --print-architecture); \
+    curl -fsSL "https://github.com/golangci/golangci-lint/releases/download/${GOLANGCI_LINT_VERSION}/golangci-lint-${GOLANGCI_LINT_VERSION#v}-linux-${ARCH}.tar.gz" \
+    | tar -xzC /usr/local/bin --strip-components=1 \
+      "golangci-lint-${GOLANGCI_LINT_VERSION#v}-linux-${ARCH}/golangci-lint"

docs/development.md

@@ -41,11 +41,11 @@ The embedded Dockerfile defines an Ubuntu 24.04 base image. Exact versions are p
 
 | Category | Tools |
 |----------|-------|
-| Runtimes | Go, Node.js, Bun, Python 3 + uv |
-| Package managers | npm, Yarn (via corepack), Homebrew |
-| Language servers | gopls, typescript-language-server, pyright, yaml-language-server, bash-language-server, jsonnet-language-server, helm-ls |
-| CLI tools | Docker CLI, ripgrep, fd, fzf, jq, vim, git, openssh-client |
-| Agent stack | OpenCode, oh-my-openagent |
+| Runtimes | Node.js, Python 3 |
+| Package managers | npm |
+| Language servers | typescript-language-server, pyright, yaml-language-server, bash-language-server |
+| CLI tools | ripgrep, fd, jq, git, openssh-client, curl |
+| Agent stack | OpenCode |
 
 Source: [`internal/embed/assets/Dockerfile`](https://github.com/seznam/jailoc/blob/master/internal/embed/assets/Dockerfile)
 
@@ -86,3 +86,17 @@ One file per package concern: `docker.go`, `compose.go`, `workspace.go`, `config
 ### Testing
 
 Unit tests live beside their source files as `*_test.go`. Integration tests live in `internal/integration_test.go` and require the `//go:build integration` build tag. Tests use `t.Parallel()` and a table-driven style with `t.Run`. There are no mocks, fixtures, or testdata directories.
+
+## Developing inside a jailoc container
+
+`dev/Dockerfile.jailoc` is a workspace overlay that extends the default image with the Go toolchain, gopls, and golangci-lint. It lets you develop jailoc inside a jailoc container.
+
+Add to `~/.config/jailoc/config.toml`:
+
+```toml
+[workspaces.jailoc]
+paths = ["/path/to/jailoc"]
+dockerfile = "https://raw.githubusercontent.com/seznam/jailoc/main/dev/Dockerfile.jailoc"
+```
+
+Then run `jailoc up jailoc`. The standard build and test commands work inside the container unchanged.