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// 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
sort.Slice(entries, func(i, j int) bool {
nameI, nameJ := entries[i].name, entries[j].name
if nameI == nameJ { // meh
return !(entries[i].mode == "40000") && (entries[j].mode == "40000")
}
if strings.HasPrefix(nameJ, nameI) && len(nameI) < len(nameJ) {
if entries[i].mode == "40000" {
return false
}
return true
}
if strings.HasPrefix(nameI, nameJ) && len(nameJ) < len(nameI) {
// nameJ is a prefix of nameI
if entries[j].mode == "40000" {
return true
}
return false
}
return nameI < nameJ
})
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
}
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