update env var expansion logic

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2026-01-18 02:29:26 -05:00
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# AGENTS.md
Agent guide for the `mg` codebase - a Go replacement for [myrepos](https://myrepos.branchable.com/) that only supports git repos.
## Project Overview
`mg` is a CLI tool for managing multiple git repositories simultaneously. It uses `go-git/go-git` for pure Go git operations (no external git dependency required) and `spf13/cobra` for CLI structure.
### Key Features
- Parallel operations via `-j` flag
- Compatible with existing `~/.mrconfig` files (auto-migrates to `mgconfig`)
- Pure Go implementation - no external git binary needed
- Embeddable as a library
## Commands
```bash
# Build
go build ./...
# Run tests
go test ./...
# Install the binary
go install ./cmd/mg
# Run directly
go run ./cmd/mg <command>
```
## Project Structure
```
mg/
├── cmd/
│ ├── mg/
│ │ ├── main.go # Entry point
│ │ └── cmd/ # Cobra commands
│ │ ├── root.go # Root command setup
│ │ ├── common.go # Shared utilities (GetConfig)
│ │ ├── clone.go # Clone all repos (implemented)
│ │ ├── pull.go # Pull all repos (implemented)
│ │ ├── register.go # Register repo (implemented)
│ │ ├── unregister.go# Unregister repo (implemented)
│ │ ├── import.go # Merge configs (implemented)
│ │ ├── push.go # Stub
│ │ ├── fetch.go # Stub
│ │ ├── status.go # Stub
│ │ ├── diff.go # Stub
│ │ ├── commit.go # Stub
│ │ └── config.go # Stub
│ └── paths/
│ └── mrpaths.go # Utility to list repo paths from mrconfig
└── parse/
├── mgconf.go # MGConfig: JSON-based config format
├── myrepos.go # MRConfig: Parse ~/.mrconfig (INI-style)
└── myrepos_test.go # Tests (skeleton)
```
## Implementation Status
| Command | Status | Notes |
|--------------|-------------|------------------------------------|
| `clone` | Implemented | Parallel via `-j`, creates dirs |
| `pull` | Implemented | Parallel via `-j` |
| `register` | Implemented | Detects git root, stores `$HOME` |
| `unregister` | Implemented | By path or current dir |
| `import` | Implemented | Merge configs, supports stdin `-` |
| `push` | Stub | Prints "push called" |
| `fetch` | Stub | Prints "fetch called" |
| `status` | Stub | Prints "status called" |
| `diff` | Stub | Prints "diff called" |
| `commit` | Stub | Prints "commit called" |
| `config` | Stub | Prints "config called" |
## Configuration
### Config File Location
1. `$MGCONFIG` environment variable (if set)
2. `$XDG_CONFIG_HOME/mgconfig`
3. `~/.config/mgconfig`
### Config Format (JSON)
```json
{
"Repos": [
{
"Path": "$HOME/code/project",
"Remote": "git@github.com:user/project.git"
}
],
"Aliases": {}
}
```
### Migration from myrepos
If no `mgconfig` exists but `~/.mrconfig` does, `mg` auto-migrates on first run. The `MRConfig.ToMGConfig()` method handles conversion.
## Code Patterns
### Adding a New Command
1. Create `cmd/mg/cmd/<name>.go`
2. Define a `cobra.Command` variable
3. Register in `init()` via `rootCmd.AddCommand()`
4. For parallel operations, follow the pattern in `clone.go` or `pull.go`:
```go
var myCmd = &cobra.Command{
Use: "mycommand",
Short: "description",
Run: func(_ *cobra.Command, args []string) {
conf := GetConfig() // Load config with fallback to mrconfig
// Implementation...
},
}
func init() {
rootCmd.AddCommand(myCmd)
myCmd.Flags().IntVarP(&jobs, "jobs", "j", 1, "number of parallel jobs")
}
```
### Parallel Execution Pattern
Used in `clone.go` and `pull.go`:
```go
repoChan := make(chan RepoType, len(repos))
wg := sync.WaitGroup{}
mutex := sync.Mutex{}
errs := []Error{}
wg.Add(len(repos))
for i := 0; i < jobs; i++ {
go func() {
for repo := range repoChan {
// Do work
// Use mutex for shared state (errs, counters)
wg.Done()
}
}()
}
for _, repo := range repos {
repoChan <- repo
}
close(repoChan)
wg.Wait()
```
### Git Operations
Use `go-git/go-git/v5`:
```go
import git "github.com/go-git/go-git/v5"
// Open repo (detects .git in parent dirs)
r, err := git.PlainOpenWithOptions(path, &git.PlainOpenOptions{DetectDotGit: true})
// Clone
_, err = git.PlainClone(path, false, &git.CloneOptions{URL: remote})
// Pull
w, _ := r.Worktree()
err = w.Pull(&git.PullOptions{})
// Check: err == git.NoErrAlreadyUpToDate
```
### Path Handling
- Paths in config use `$HOME` prefix for portability
- `GetConfig()` in `common.go` expands `$HOME` to actual home directory at runtime
- `register` command stores paths with `$HOME` prefix
## Key Types
### `parse.MGConfig`
```go
type MGConfig struct {
Repos []Repo
Aliases map[string]string
}
// Methods
func LoadMGConfig() (MGConfig, error)
func (m *MGConfig) AddRepo(path, remote string) error
func (m *MGConfig) DelRepo(path string) error
func (m *MGConfig) Merge(m2 MGConfig) (Stats, error)
func (m MGConfig) Save() error
```
### `parse.Repo`
```go
type Repo struct {
Path string
Remote string
Aliases map[string]string `json:"aliases,omitempty"`
}
```
## Dependencies
- `github.com/go-git/go-git/v5` - Pure Go git implementation
- `github.com/spf13/cobra` - CLI framework
## Testing
Tests are minimal. Only `parse/myrepos_test.go` exists with a skeleton structure:
```bash
go test ./...
```
## Known Issues / TODOs
1. Several commands are stubs (push, fetch, status, diff, commit, config)
2. `parse/mgconf.go:61` has a hint about inefficient string concatenation in a loop
3. Test coverage is minimal
4. `unregister` command short description incorrectly says "add current path" (copy-paste error)
## Error Handling Pattern
Commands typically:
1. Log errors via `log.Println(err)`
2. Exit with `os.Exit(1)` on fatal errors
3. Collect errors during parallel operations and report summary at end