LMTP: Actually apply patches from email

1 files changed, 173 insertions, 0 deletions

diff --git a/git_plumbing.go b/git_plumbing.go
new file mode 100644
index 0000000..36acb90
--- /dev/null
+++ b/git_plumbing.go
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/hex"
+	"errors"
+	"os"
+	"os/exec"
+	"path"
+	"sort"
+	"strings"
+)
+
+func writeTree(ctx context.Context, repoPath string, entries []treeEntry) (string, error) {
+	var buf bytes.Buffer
+
+	// Must
+	sort.Slice(entries, func(i, j int) bool {
+		return entries[i].name < entries[j].name
+	})
+
+	for _, e := range entries {
+		buf.WriteString(e.mode)
+		buf.WriteByte(' ')
+		buf.WriteString(e.name)
+		buf.WriteByte(0)
+		buf.Write(e.sha)
+	}
+
+	cmd := exec.CommandContext(ctx, "git", "hash-object", "-w", "-t", "tree", "--stdin")
+	cmd.Env = append(os.Environ(), "GIT_DIR="+repoPath)
+	cmd.Stdin = &buf
+
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(out.String()), nil
+}
+
+func buildTreeRecursive(ctx context.Context, repoPath string, baseTree string, updates map[string][]byte) (string, error) {
+	treeCache := make(map[string][]treeEntry)
+
+	var walk func(string, string) error
+	walk = func(prefix, sha string) error {
+		cmd := exec.CommandContext(ctx, "git", "cat-file", "tree", sha)
+		cmd.Env = append(os.Environ(), "GIT_DIR="+repoPath)
+		var out bytes.Buffer
+		cmd.Stdout = &out
+		if err := cmd.Run(); err != nil {
+			return err
+		}
+		data := out.Bytes()
+		i := 0
+		var entries []treeEntry
+		for i < len(data) {
+			modeEnd := bytes.IndexByte(data[i:], ' ')
+			if modeEnd < 0 {
+				return errors.New("invalid tree format")
+			}
+			mode := string(data[i : i+modeEnd])
+			i += modeEnd + 1
+
+			nameEnd := bytes.IndexByte(data[i:], 0)
+			if nameEnd < 0 {
+				return errors.New("missing null after filename")
+			}
+			name := string(data[i : i+nameEnd])
+			i += nameEnd + 1
+
+			if i+20 > len(data) {
+				return errors.New("unexpected EOF in SHA")
+			}
+			shaBytes := data[i : i+20]
+			i += 20
+
+			entries = append(entries, treeEntry{
+				mode: mode,
+				name: name,
+				sha:  shaBytes,
+			})
+
+			if mode == "40000" {
+				subPrefix := path.Join(prefix, name)
+				if err := walk(subPrefix, hex.EncodeToString(shaBytes)); err != nil {
+					return err
+				}
+			}
+		}
+		treeCache[prefix] = entries
+		return nil
+	}
+
+	if err := walk("", baseTree); err != nil {
+		return "", err
+	}
+
+	for filePath, blobSha := range updates {
+		parts := strings.Split(filePath, "/")
+		dir := strings.Join(parts[:len(parts)-1], "/")
+		name := parts[len(parts)-1]
+
+		entries := treeCache[dir]
+		found := false
+		for i, e := range entries {
+			if e.name == name {
+				if blobSha == nil {
+					// Remove TODO
+					entries = append(entries[:i], entries[i+1:]...)
+				} else {
+					entries[i].sha = blobSha
+				}
+				found = true
+				break
+			}
+		}
+		if !found && blobSha != nil {
+			entries = append(entries, treeEntry{
+				mode: "100644",
+				name: name,
+				sha:  blobSha,
+			})
+		}
+		treeCache[dir] = entries
+	}
+
+	built := make(map[string][]byte)
+	var build func(string) ([]byte, error)
+	build = func(prefix string) ([]byte, error) {
+		entries := treeCache[prefix]
+		for i, e := range entries {
+			if e.mode == "40000" {
+				subPrefix := path.Join(prefix, e.name)
+				if sha, ok := built[subPrefix]; ok {
+					entries[i].sha = sha
+					continue
+				}
+				newShaStr, err := build(subPrefix)
+				if err != nil {
+					return nil, err
+				}
+				entries[i].sha = newShaStr
+			}
+		}
+		shaStr, err := writeTree(ctx, repoPath, entries)
+		if err != nil {
+			return nil, err
+		}
+		shaBytes, err := hex.DecodeString(shaStr)
+		if err != nil {
+			return nil, err
+		}
+		built[prefix] = shaBytes
+		return shaBytes, nil
+	}
+
+	rootShaBytes, err := build("")
+	if err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(rootShaBytes), nil
+}
+
+type treeEntry struct {
+	mode string // like "100644"
+	name string // individual name
+	sha  []byte
+}