pama: implement the revision control logic

Implement the RevisionController interface to interact with a
respository control system. Add the implementation for git. Other
revision systems such as mercurial, pijul or fossil can be extended.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

2 files changed, 160 insertions, 0 deletions

diff --git a/lib/pama/revctrl/git.go b/lib/pama/revctrl/git.go
new file mode 100644
index 00000000..f4b78dd5
--- /dev/null
+++ b/lib/pama/revctrl/git.go
@@ -0,0 +1,112 @@
+package revctrl
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/lib/pama/models"
+	"git.sr.ht/~rjarry/aerc/log"
+)
+
+func init() {
+	register("git", newGit)
+}
+
+func newGit(s string) models.RevisionController {
+	return &git{path: strings.TrimSpace(s)}
+}
+
+type git struct {
+	path string
+}
+
+func (g git) Support() bool {
+	_, exitcode, err := g.do("rev-parse")
+	return exitcode == 0 && err == nil
+}
+
+func (g git) Root() (string, error) {
+	s, _, err := g.do("rev-parse", "--show-toplevel")
+	return s, err
+}
+
+func (g git) Head() (string, error) {
+	s, _, err := g.do("rev-list", "-n 1", "HEAD")
+	return s, err
+}
+
+func (g git) History(commit string) ([]string, error) {
+	s, _, err := g.do("rev-list", "--reverse", fmt.Sprintf("%s..HEAD", commit))
+	return strings.Fields(s), err
+}
+
+func (g git) Subject(commit string) string {
+	s, exitcode, err := g.do("log", "-1", "--pretty=%s", commit)
+	if exitcode > 0 || err != nil {
+		return ""
+	}
+	return s
+}
+
+func (g git) Author(commit string) string {
+	s, exitcode, err := g.do("log", "-1", "--pretty=%an", commit)
+	if exitcode > 0 || err != nil {
+		return ""
+	}
+	return s
+}
+
+func (g git) Date(commit string) string {
+	s, exitcode, err := g.do("log", "-1", "--pretty=%as", commit)
+	if exitcode > 0 || err != nil {
+		return ""
+	}
+	return s
+}
+
+func (g git) Remove(commit string) error {
+	_, exitcode, err := g.do("rebase", "--onto", commit+"^", commit)
+	if exitcode > 0 {
+		return fmt.Errorf("failed to remove commit %s", commit)
+	}
+	return err
+}
+
+func (g git) Exists(commit string) bool {
+	_, exitcode, err := g.do("merge-base", "--is-ancestor", commit, "HEAD")
+	return exitcode == 0 && err == nil
+}
+
+func (g git) Clean() bool {
+	// is a rebase in progress?
+	dirs := []string{"rebase-merge", "rebase-apply"}
+	for _, dir := range dirs {
+		relPath, _, err := g.do("rev-parse", "--git-path", dir)
+		if err == nil {
+			if _, err := os.Stat(filepath.Join(g.path, relPath)); !os.IsNotExist(err) {
+				log.Errorf("%s exists: another rebase in progress..", dir)
+				return false
+			}
+		}
+	}
+	// are there unstaged changes?
+	s, exitcode, err := g.do("diff-index", "HEAD")
+	return len(s) == 0 && exitcode == 0 && err == nil
+}
+
+func (g git) ApplyCmd() string {
+	// TODO: should we return a *exec.Cmd instead of a string?
+	return fmt.Sprintf("git -C %s am -3 --empty drop", g.path)
+}
+
+func (g git) do(args ...string) (string, int, error) {
+	proc := exec.Command("git", "-C", g.path)
+	proc.Args = append(proc.Args, args...)
+	proc.Env = os.Environ()
+	result, err := proc.Output()
+	return string(bytes.TrimSpace(result)), proc.ProcessState.ExitCode(), err
+}
diff --git a/lib/pama/revctrl/revctrl.go b/lib/pama/revctrl/revctrl.go
new file mode 100644
index 00000000..42532216
--- /dev/null
+++ b/lib/pama/revctrl/revctrl.go
@@ -0,0 +1,48 @@
+package revctrl
+
+import (
+	"errors"
+	"fmt"
+
+	"git.sr.ht/~rjarry/aerc/lib/pama/models"
+	"git.sr.ht/~rjarry/aerc/log"
+)
+
+var ErrUnsupported = errors.New("unsupported")
+
+type factoryFunc func(string) models.RevisionController
+
+var controllers = map[string]factoryFunc{}
+
+func register(controllerID string, fn factoryFunc) {
+	controllers[controllerID] = fn
+}
+
+func New(controllerID string, path string) (models.RevisionController, error) {
+	factoryFunc, ok := controllers[controllerID]
+	if !ok {
+		return nil, errors.New("cannot create revision control instance")
+	}
+	return factoryFunc(path), nil
+}
+
+type detector interface {
+	Support() bool
+	Root() (string, error)
+}
+
+func Detect(path string) (string, string, error) {
+	for controllerID, factoryFunc := range controllers {
+		rc, ok := factoryFunc(path).(detector)
+		if ok && rc.Support() {
+			log.Tracef("support found for %v", controllerID)
+			root, err := rc.Root()
+			if err != nil {
+				continue
+			}
+			log.Tracef("root found in %s", root)
+			return controllerID, root, nil
+		}
+	}
+	return "", "", fmt.Errorf("no supported repository found in %s", path)
+}