1// SPDX-License-Identifier: AGPL-3.0-or-later
2
3package gitcli
4
5import (
6 "context"
7 "fmt"
8 "os"
9 "path/filepath"
10 "strconv"
11 "strings"
12
13 "bnema.dev/ermite/internal/domain"
14 "bnema.dev/ermite/internal/ports"
15)
16
17var _ ports.GitBackend = (*Git)(nil)
18
19// backendOwner is REMOTE_USER of a push: ermite authorizes before Git runs,
20// so Git only needs to see a user.
21const backendOwner = "owner"
22
23// HooksDir is the directory, below the data root, that holds the hook
24// scripts every receive-pack runs.
25func HooksDir(dataDir string) string { return filepath.Join(dataDir, "run", "hooks") }
26
27// HTTPBackend resolves git-http-backend through `git --exec-path` of the
28// configured git (once), and builds its environment: the isolated one,
29// GIT_PROJECT_ROOT=<data>/repos, GIT_HTTP_EXPORT_ALL and the configuration
30// passed by GIT_CONFIG_COUNT/KEY/VALUE, so that nothing is written to the
31// repositories:
32//
33// core.hooksPath=<data>/run/hooks
34// receive.fsckObjects=true
35// uploadpack.allowFilter=true
36// pack.threads=1
37// pack.windowMemory=256m
38// http.receivepack=true (push only)
39// receive.hideRefs=refs/pull/ (push only: ermite writes them, git refuses updates)
40// receive.maxInputSize=<max> (push only, when configured)
41//
42// A push also gets REMOTE_USER=owner.
43func (g *Git) HTTPBackend(ctx context.Context, push bool) (ports.HTTPBackend, error) {
44 path, err := g.backendPath(ctx)
45 if err != nil {
46 return ports.HTTPBackend{}, err
47 }
48 conf := [][2]string{
49 {"core.hooksPath", HooksDir(g.dataDir)},
50 {"receive.fsckObjects", "true"},
51 {"uploadpack.allowFilter", "true"},
52 // pack-objects defaults to one thread per CPU and an unbounded delta
53 // window; with several backends at once that is the memory and CPU
54 // of the host. The backends are bounded by the handler instead.
55 {"pack.threads", "1"},
56 {"pack.windowMemory", "256m"},
57 }
58 if push {
59 conf = append(conf, [2]string{"http.receivepack", "true"})
60 // refs/pull/* (the merge requests' head and test merge) are served to
61 // fetch and cannot be updated by a push: git itself refuses a hidden ref.
62 conf = append(conf, [2]string{"receive.hideRefs", domain.PullRefPrefix})
63 if g.maxRecv > 0 {
64 conf = append(conf, [2]string{"receive.maxInputSize", strconv.FormatInt(g.maxRecv, 10)})
65 }
66 }
67 env := append([]string(nil), g.env...)
68 env = append(env,
69 "GIT_PROJECT_ROOT="+g.reposDir(),
70 "GIT_HTTP_EXPORT_ALL=1",
71 "GIT_CONFIG_COUNT="+strconv.Itoa(len(conf)),
72 )
73 for i, kv := range conf {
74 n := strconv.Itoa(i)
75 env = append(env, "GIT_CONFIG_KEY_"+n+"="+kv[0], "GIT_CONFIG_VALUE_"+n+"="+kv[1])
76 }
77 if push {
78 env = append(env, "REMOTE_USER="+backendOwner)
79 }
80 return ports.HTTPBackend{Path: path, Dir: g.reposDir(), Env: env}, nil
81}
82
83// backendPath returns <git --exec-path>/git-http-backend, cached after the
84// first success.
85func (g *Git) backendPath(ctx context.Context) (string, error) {
86 g.mu.Lock()
87 defer g.mu.Unlock()
88 if g.backend != "" {
89 return g.backend, nil
90 }
91 out, err := g.run(ctx, "--exec-path")
92 if err != nil {
93 return "", fmt.Errorf("find git exec path: %w", err)
94 }
95 execPath := strings.TrimSpace(out)
96 if execPath == "" {
97 return "", fmt.Errorf("find git exec path: git printed nothing")
98 }
99 path := filepath.Join(execPath, "git-http-backend")
100 fi, err := os.Stat(path)
101 if err != nil {
102 return "", fmt.Errorf("find git-http-backend: %w", err)
103 }
104 if fi.IsDir() || fi.Mode().Perm()&0o111 == 0 {
105 return "", fmt.Errorf("find git-http-backend: %s is not an executable", path)
106 }
107 g.backend = path
108 return path, nil
109}