Upload GitHub Attachment

1#!/usr/bin/env bash
2# Upload one local file to GitHub user-attachments and print its URL.
3# Fallback for GitHub CLI versions without `gh pr create --attach`.
4set -euo pipefail
5
6usage() {
7  printf 'Usage: %s [--repo OWNER/REPO] [--content-type MIME] FILE\n' "$(basename "$0")"
8}
9
10repository=''
11content_type=''
12attachment_file=''
13
14while (($# > 0)); do
15  case "$1" in
16    --repo) repository="${2:-}"; shift 2 ;;
17    --content-type) content_type="${2:-}"; shift 2 ;;
18    -h|--help) usage; exit 0 ;;
19    --*) printf 'Unknown option: %s\n' "$1" >&2; usage >&2; exit 2 ;;
20    *)
21      if [[ -n "$attachment_file" ]]; then
22        printf 'Only one file can be uploaded per invocation.\n' >&2
23        exit 2
24      fi
25      attachment_file="$1"; shift ;;
26  esac
27done
28
29for tool in gh curl; do
30  if ! command -v "$tool" >/dev/null 2>&1; then
31    printf '%s is required.\n' "$tool" >&2
32    exit 127
33  fi
34done
35
36if [[ -z "$attachment_file" || ! -f "$attachment_file" ]]; then
37  printf 'Provide one existing local file.\n' >&2
38  usage >&2
39  exit 2
40fi
41
42if [[ -z "$repository" ]]; then
43  repository="$(gh repo view --json nameWithOwner --jq .nameWithOwner 2>/dev/null || true)"
44fi
45if [[ -z "$repository" ]]; then
46  printf 'Could not resolve a GitHub repository. Run inside a checkout or pass --repo OWNER/REPO.\n' >&2
47  exit 2
48fi
49
50token="${GH_TOKEN:-${GITHUB_TOKEN:-}}"
51if [[ -z "$token" ]]; then
52  token="$(gh auth token 2>/dev/null || true)"
53fi
54if [[ -z "$token" ]]; then
55  printf 'GitHub authentication is required. Run gh auth login or set GH_TOKEN/GITHUB_TOKEN.\n' >&2
56  exit 1
57fi
58
59if [[ -z "$content_type" ]]; then
60  if ! command -v file >/dev/null 2>&1; then
61    printf 'The file utility is required for MIME detection; install it or pass --content-type.\n' >&2
62    exit 127
63  fi
64  content_type="$(file --brief --mime-type "$attachment_file")"
65fi
66
67repository_id="$(GH_TOKEN="$token" gh api "repos/$repository" --jq .id)"
68
69# Undocumented endpoint, observed from the web UI upload flow.
70response="$(curl --silent --show-error --fail-with-body \
71  --request POST \
72  --header "Authorization: Bearer $token" \
73  --header 'Accept: application/json' \
74  --url-query "name=$(basename "$attachment_file")" \
75  --url-query "content_type=$content_type" \
76  --url-query "repository_id=$repository_id" \
77  --data-binary "@$attachment_file" \
78  'https://uploads.github.com/user-attachments/assets')"
79
80attachment_url="$(printf '%s' "$response" | sed -n 's/.*"url"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p')"
81if [[ "$attachment_url" != https://github.com/user-attachments/* ]]; then
82  printf 'GitHub did not return a user-attachment URL.\n' >&2
83  exit 1
84fi
85
86printf '%s\n' "$attachment_url"