Add a function to find the /git-artifacts PR comment for a given commit SHA

To update the `/git-artifacts` comment when cascading
`git-artifacts-<arch>` runs are triggered, we need a way to get from the
commit SHA (which is part of the `check_run.completed` webhook) to the
corresponding PR comment ID.

Here, we introduce a function to do that, by using GitHub API's search
functionality. The commit SHA is given verbatim, which should be good
enough according to the documentation at
https://docs.github.com/en/search-github/searching-on-github/searching-issues-and-pull-requests#search-by-commit-sha

Further, we make use of the text match metadata
(https://docs.github.com/en/rest/search/search#text-match-metadata) to
match the desired PR comment and to extract the PR comment ID.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

GitForWindowsHelper/github-api-request.js

@@ -1,6 +1,8 @@
-module.exports = async (context, token, method, requestPath, payload) => {
+module.exports = async (context, token, method, requestPath, payload, extraHeaders) => {
     const { httpsRequest } = require('./https-request')
-    const headers = token ? { Authorization: `Bearer ${token}` } : null
+    const headers = token
+        ? { ...(extraHeaders || {}), Authorization: `Bearer ${token}` }
+        : extraHeaders
     const answer = await httpsRequest(context, null, method, requestPath, payload, headers)
     if (answer.error) throw answer.error
     return answer

GitForWindowsHelper/issues.js

@@ -23,6 +23,17 @@ const getIssueComment = async (context, token, owner, repo, comment_id) => {
     return await sendGitHubAPIRequest(context, token, 'GET', `/repos/${owner}/${repo}/issues/comments/${comment_id}`)
 }
 
+const getGitArtifactsCommentID = async (context, token, owner, repo, headSHA) => {
+    const answer = await sendGitHubAPIRequest(context, token, 'GET', `/search/issues?q=repo:${owner}/${repo}+${headSHA}+type:pr+%22git-artifacts%22`, null, {
+        Accept: 'application/vnd.github.text-match+json'
+    })
+    const items = answer.items.filter(item =>
+        item.text_matches.length === 1
+        && item.text_matches[0].fragment === '/git-artifacts\n\nThe tag-git workflow run was started\n'
+    )
+    return items.length === 1 && items[0].text_matches[0].object_url.replace(/^.*\/(\d+)$/, '$1')
+}
+
 const appendToIssueComment = async (context, token, owner, repo, comment_id, append) => {
     const data = await getIssueComment(context, token, owner, repo, comment_id)
     const answer = await sendGitHubAPIRequest(
@@ -65,6 +76,7 @@ const getPRCommitSHA = async (context, token, owner, repo, pullRequestNumber) =>
 module.exports = {
     addIssueComment,
     getIssue,
+    getGitArtifactsCommentID,
     getIssueComment,
     appendToIssueComment,
     createReactionForIssueComment,