feat(app): support git-URL recipes in 'abra app new'

Allow `abra app new <git-url>` to use a recipe from outside the
catalogue. On clone, a `.abra-source` sidecar records the canonical
host/path name (the on-disk directory escapes "/" and "." lossily), and
IsClean ignores it. When templating the app's .env, a `RECIPE=<canonical
name>` line is injected so a later `abra app deploy`, possibly on another
machine, re-fetches the recipe from the same git source. `recipe ls` now
shows a source column listing these external recipes alongside catalogue
ones.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pkg/git/read.go

@@ -36,6 +36,11 @@ func IsClean(repoPath string) (bool, error) {
 		return false, err
 	}
 
+	// Ignore the abra-managed sidecar file that records the canonical
+	// source URL for externally-cloned recipes; it lives alongside the
+	// recipe but is not part of the upstream tree.
+	patterns = append(patterns, gitignore.ParsePattern(".abra-source", nil))
+
 	if len(patterns) > 0 {
 		worktree.Excludes = append(patterns, worktree.Excludes...)
 	}

pkg/git/read_test.go

@@ -2,6 +2,8 @@ package git
 
 import (
 	"errors"
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/go-git/go-git/v5"
@@ -13,3 +15,37 @@ func TestIsClean(t *testing.T) {
 	assert.Equal(t, isClean, false)
 	assert.True(t, errors.Is(err, git.ErrRepositoryNotExists))
 }
+
+// TestIsCleanIgnoresAbraSource confirms that the .abra-source sidecar
+// file written by abra next to externally-cloned recipes does not cause
+// IsClean to report the worktree as dirty.
+func TestIsCleanIgnoresAbraSource(t *testing.T) {
+	dir := t.TempDir()
+
+	if _, err := git.PlainInit(dir, false); err != nil {
+		t.Fatalf("git init failed: %s", err)
+	}
+
+	sidecar := filepath.Join(dir, ".abra-source")
+	if err := os.WriteFile(sidecar, []byte("git.example.com/u/recipe\n"), 0o644); err != nil {
+		t.Fatalf("writing sidecar failed: %s", err)
+	}
+
+	isClean, err := IsClean(dir)
+	if err != nil {
+		t.Fatalf("IsClean returned error: %s", err)
+	}
+	assert.True(t, isClean, "expected worktree with only .abra-source to be reported clean")
+
+	// Sanity check: an unrelated untracked file should still mark it dirty.
+	other := filepath.Join(dir, "random.txt")
+	if err := os.WriteFile(other, []byte("hello"), 0o644); err != nil {
+		t.Fatalf("writing extra file failed: %s", err)
+	}
+
+	isClean, err = IsClean(dir)
+	if err != nil {
+		t.Fatalf("IsClean returned error: %s", err)
+	}
+	assert.False(t, isClean, "expected worktree with unrelated untracked file to be reported dirty")
+}