Convert commands and context to skills, add skills symlinks to Rexfile

Move purge-file-from-git, compose-blog-post, increment-version-and-push
from commands to skills format, and convert go-best-practices from context
to a skill. Update Rexfile home_prompts task to symlink both commands and
skills directories for cursor, claude, agents, and opencode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 81 insertions, 0 deletions

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+---
+name: go-best-practices
+description: Enforce Go best practices for project structure, style, and conventions in the current codebase.
+---
+
+# Go Best Practices
+
+Enforce Go project structure, style, and conventions in the current codebase.
+
+## When to Use
+
+- Use this skill when working on a Go project to ensure the code follows the established best practices.
+- Use this skill to review or refactor existing Go code for compliance.
+
+## Instructions
+
+When writing or modifying Go code in the current project, follow all of the conventions below.
+
+### Semantics and receivers
+
+* Prefer value semantics over pointer semantics if feasible
+* Have either pointer or value receivers, not both, for methods on a type
+
+### File layout and order
+
+* Constants, global variables, and type definitions always at the top of the file, before functions and methods
+* Public functions and methods before private ones in the file
+* Constructors must be the first functions in a file (before all methods), immediately after type definitions—even if non-public
+
+### Project structure
+
+* Binary is in `./cmd/NAME/main.go`
+* Main file should be fairly small: argument/flags parsing and calling functions from the internal package only
+* Internal code is in `./internal`
+* Version of the app is a constant in `./internal/version.go`; a `-version` flag in main.go prints it out
+
+### Dependencies and I/O
+
+* Avoid package-level variables unless absolutely necessary; prefer dependency injection
+* Use `context.Context` as the first parameter for functions that may block, perform I/O, or be canceled
+* Use `defer` to close resources (files, connections) as soon as they are opened
+
+### Errors and interfaces
+
+* Use error wrapping (`fmt.Errorf` with `%w`) to provide context for errors
+* Prefer explicit interface satisfaction for public types: `var _ MyInterface = (*MyType)(nil)`
+* Keep interfaces small and focused; accept interfaces, return concrete types
+
+### Formatting and documentation
+
+* Use `gofmt` and `goimports` to enforce formatting and import order
+* Document all exported identifiers with comments starting with the identifier's name
+* Avoid stutter in package and type names (e.g. `foo.FooType` → `foo.Type`)
+
+### Naming and constants
+
+* Short variable names for short-lived variables, longer names for longer-lived ones
+* Use `iota` for related constant values
+
+### Testing and robustness
+
+* Use table-driven tests for unit testing
+* Aim for unit test coverage of 60%
+* Avoid `panic` except for truly unrecoverable errors (e.g. programmer errors)
+* Avoid large functions; split into smaller, focused helpers (max ~50 lines per function)
+* Avoid code duplication where reasonable
+
+### Build system
+
+Use Mage (Magefile.go) for build, install and test targets (and deinstall/uninstall when needed).
+
+#### Magefile.go structure
+
+* **Build tag and package:** `//go:build mage` at top; `package main`. Brief comment describing the project and that targets follow the same style as other projects (e.g. hexai) if applicable.
+* **Imports:** `github.com/magefile/mage/mg`, `github.com/magefile/mage/sh`; plus stdlib as needed (`fmt`, `os`, `path/filepath`).
+* **Constants:** Define `binaryName` (or equivalent) for the built binary.
+* **Default target:** `Default()` calls `mg.Deps(Build)` so `mage` with no args builds.
+* **Build:** `Build()` runs `go build -o <binaryName> ./cmd/<name>` via `sh.RunV`.
+* **Test:** `Test()` runs `go test ./...` via `sh.RunV`.
+* **Install:** `Install()` depends on `Build` via `mg.Deps(Build)`; resolves GOPATH (default `~/go` when unset); ensures `GOPATH/bin` exists with `os.MkdirAll`; copies the binary there with `cp -v`. Use `fmt.Errorf` with `%w` for errors (e.g. resolving home).
+* **Other targets:** Add Uninstall/Deinstall or custom targets as needed; keep the same style (mg.Deps for ordering, sh.RunV for external commands).