A shepherd for your Appimages.
only write icons + desktop files if modified
Aly Raffauf
(Jun 17, 2026, 6:21 PM EDT)
9f4fbbda
4662baef
+91
-12
+1
-5
cmd/appherder/desktop.go
+1
-5
cmd/appherder/desktop.go
···
3
3
import (
4
4
"errors"
5
5
"fmt"
6
-
"io"
7
6
"io/fs"
8
7
"os"
9
8
"path/filepath"
···
237
236
if d.trailingNewline {
238
237
text += "\n"
239
238
}
240
-
return writeAtomic(path, 0o644, func(w io.Writer) error {
241
-
_, err := w.Write([]byte(text))
242
-
return err
243
-
})
239
+
return writeIfChanged(path, 0o644, []byte(text))
244
240
}
245
241
246
242
func (a app) patchDesktopFile(desktop *desktopFile, appName string, hasIcon bool) error {
+18
-7
cmd/appherder/files.go
+18
-7
cmd/appherder/files.go
···
10
10
"path/filepath"
11
11
)
12
12
13
+
// writeIfChanged writes content to path atomically, but skips when path
14
+
// already holds identical bytes so the file's mtime stays stable.
15
+
func writeIfChanged(path string, perm os.FileMode, content []byte) error {
16
+
if existing, err := os.ReadFile(path); err == nil {
17
+
if bytes.Equal(existing, content) {
18
+
return nil
19
+
}
20
+
} else if !errors.Is(err, os.ErrNotExist) {
21
+
return err
22
+
}
23
+
return writeAtomic(path, perm, func(w io.Writer) error {
24
+
_, err := w.Write(content)
25
+
return err
26
+
})
27
+
}
28
+
13
29
// writeAtomic writes via a temp file beside path and renames it into place, so
14
30
// path never holds a partially written file.
15
31
func writeAtomic(path string, perm os.FileMode, write func(io.Writer) error) (err error) {
···
81
97
}
82
98
83
99
func copyFromFS(fsys fs.FS, name string, dest string) error {
84
-
in, err := fsys.Open(name)
100
+
content, err := fs.ReadFile(fsys, name)
85
101
if err != nil {
86
102
return err
87
103
}
88
-
defer in.Close()
89
-
90
-
return writeAtomic(dest, 0o644, func(w io.Writer) error {
91
-
_, err := io.Copy(w, in)
92
-
return err
93
-
})
104
+
return writeIfChanged(dest, 0o644, content)
94
105
}
+72
cmd/appherder/files_test.go
+72
cmd/appherder/files_test.go
···
1
+
package main
2
+
3
+
import (
4
+
"os"
5
+
"path/filepath"
6
+
"testing"
7
+
"time"
8
+
)
9
+
10
+
func TestWriteIfChangedSkipsIdenticalContent(t *testing.T) {
11
+
dir := t.TempDir()
12
+
path := filepath.Join(dir, "f")
13
+
content := []byte("hello")
14
+
15
+
if err := os.WriteFile(path, content, 0o644); err != nil {
16
+
t.Fatal(err)
17
+
}
18
+
// Pin an old mtime so a skipped write is detectable.
19
+
old := time.Unix(1000, 0)
20
+
if err := os.Chtimes(path, old, old); err != nil {
21
+
t.Fatal(err)
22
+
}
23
+
24
+
if err := writeIfChanged(path, 0o644, content); err != nil {
25
+
t.Fatal(err)
26
+
}
27
+
28
+
info, err := os.Stat(path)
29
+
if err != nil {
30
+
t.Fatal(err)
31
+
}
32
+
if !info.ModTime().Equal(old) {
33
+
t.Fatalf("mtime changed on identical write: got %v, want %v", info.ModTime(), old)
34
+
}
35
+
}
36
+
37
+
func TestWriteIfChangedWritesWhenDifferent(t *testing.T) {
38
+
dir := t.TempDir()
39
+
path := filepath.Join(dir, "f")
40
+
if err := os.WriteFile(path, []byte("old"), 0o644); err != nil {
41
+
t.Fatal(err)
42
+
}
43
+
44
+
if err := writeIfChanged(path, 0o644, []byte("new")); err != nil {
45
+
t.Fatal(err)
46
+
}
47
+
48
+
got, err := os.ReadFile(path)
49
+
if err != nil {
50
+
t.Fatal(err)
51
+
}
52
+
if string(got) != "new" {
53
+
t.Fatalf("content = %q, want new", got)
54
+
}
55
+
}
56
+
57
+
func TestWriteIfChangedCreatesWhenAbsent(t *testing.T) {
58
+
dir := t.TempDir()
59
+
path := filepath.Join(dir, "f")
60
+
61
+
if err := writeIfChanged(path, 0o644, []byte("fresh")); err != nil {
62
+
t.Fatal(err)
63
+
}
64
+
65
+
got, err := os.ReadFile(path)
66
+
if err != nil {
67
+
t.Fatal(err)
68
+
}
69
+
if string(got) != "fresh" {
70
+
t.Fatalf("content = %q, want fresh", got)
71
+
}
72
+
}