Bold questions

internal/git/changes.go

@@ -0,0 +1,144 @@
+package git
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+
+	"g.fc.run/misc/byre/internal/api"
+)
+
+var statuses = map[byte]api.FileChangeStatus{
+	'A': api.Added,
+	'M': api.Modified,
+	'D': api.Deleted,
+	'R': api.Renamed,
+	'T': api.TypeChanged,
+}
+
+func Changes(dir, defaultBranch, since string) (api.TaskChanges, error) {
+	base := since
+	if base == "" {
+		mb, err := run(dir, "merge-base", "HEAD", defaultBranch)
+		if err != nil {
+			return api.TaskChanges{}, err
+		}
+		base = mb
+	}
+
+	tree, err := Snapshot(dir)
+	if err != nil {
+		return api.TaskChanges{}, err
+	}
+
+	files, err := stats(dir, base, tree)
+	if err != nil {
+		return api.TaskChanges{}, err
+	}
+
+	return api.TaskChanges{Base: base, Tree: tree, Files: files}, nil
+}
+
+func Snapshot(dir string) (string, error) {
+	index, err := run(dir, "rev-parse", "--path-format=absolute", "--git-path", "index")
+	if err != nil {
+		return "", err
+	}
+	data, err := os.ReadFile(index)
+	if err != nil {
+		return "", err
+	}
+
+	tmp, err := os.CreateTemp("", "byre-index-*")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(tmp.Name())
+	_, err = tmp.Write(data)
+	if err != nil {
+		tmp.Close()
+		return "", err
+	}
+	err = tmp.Close()
+	if err != nil {
+		return "", err
+	}
+
+	env := []string{"GIT_INDEX_FILE=" + tmp.Name()}
+	_, err = runEnv(dir, env, "add", "--all")
+	if err != nil {
+		return "", err
+	}
+	return runEnv(dir, env, "write-tree")
+}
+
+func FileDiff(dir, base, tree, path, oldPath string) (string, error) {
+	args := []string{"diff", "--find-renames", "--no-ext-diff", "--no-color", base, tree, "--", path}
+	if oldPath != "" {
+		args = append(args, oldPath)
+	}
+	return run(dir, args...)
+}
+
+func stats(dir, base, tree string) ([]api.FileChange, error) {
+	nameStatus, err := run(dir, "diff", "--find-renames", "--name-status", "-z", base, tree)
+	if err != nil {
+		return nil, err
+	}
+	numstat, err := run(dir, "diff", "--find-renames", "--numstat", "-z", base, tree)
+	if err != nil {
+		return nil, err
+	}
+
+	counts := map[string]api.FileChange{}
+	tokens := strings.Split(numstat, "\x00")
+	for i := 0; i < len(tokens); i++ {
+		fields := strings.SplitN(tokens[i], "\t", 3)
+		if len(fields) != 3 {
+			continue
+		}
+		path := fields[2]
+		if path == "" && i+2 < len(tokens) {
+			path = tokens[i+2]
+			i += 2
+		}
+		c := api.FileChange{Binary: fields[0] == "-"}
+		c.Additions, _ = strconv.Atoi(fields[0])
+		c.Deletions, _ = strconv.Atoi(fields[1])
+		counts[path] = c
+	}
+
+	files := []api.FileChange{}
+	tokens = strings.Split(nameStatus, "\x00")
+	for i := 0; i < len(tokens); i++ {
+		code := tokens[i]
+		if code == "" {
+			continue
+		}
+		status, ok := statuses[code[0]]
+		if !ok {
+			return nil, fmt.Errorf("unknown diff status %q", code)
+		}
+		f := api.FileChange{Status: status}
+		if status == api.Renamed {
+			if i+2 >= len(tokens) {
+				return nil, fmt.Errorf("truncated rename in name-status output")
+			}
+			old := tokens[i+1]
+			f.OldPath = &old
+			f.Path = tokens[i+2]
+			i += 2
+		} else {
+			if i+1 >= len(tokens) {
+				return nil, fmt.Errorf("truncated name-status output")
+			}
+			f.Path = tokens[i+1]
+			i++
+		}
+		c := counts[f.Path]
+		f.Additions, f.Deletions, f.Binary = c.Additions, c.Deletions, c.Binary
+		files = append(files, f)
+	}
+	return files, nil
+}