feat: try SSH keys before HTTPS for github packages without protocol (#…

…852)

lib/package-managers/gitTags.js

@@ -11,12 +11,22 @@ const getSortedVersions = async (name, declaration, options) => {
   // if present, github: is parsed as the protocol. This is not valid when passed into remote-git-tags.
   declaration = declaration.replace(/^github:/, '')
   const { auth, protocol, host, path } = parseGithubUrl(declaration)
-  const url = `${protocol ? protocol.replace('git+', '') : 'https:'}//${auth ? auth + '@' : ''}${host}/${path}`
+  let tagsPromise = Promise.resolve()
+  const protocolKnown = protocol != null
+  if (protocolKnown) {
+    tagsPromise = tagsPromise.then(() => remoteGitTags(`${protocol ? protocol.replace('git+', '') : 'https:'}//${auth ? auth + '@' : ''}${host}/${path}`))
+  }
+  else {
+    // try ssh first, then https on failure
+    tagsPromise = tagsPromise.then(() => remoteGitTags(`ssh://git@${host}/${path}`))
+      .catch(() => remoteGitTags(`https://${auth ? auth + '@' : ''}${host}/${path}`))
+  }
+
   let tagMap = new Map()
 
   // fetch remote tags
   try {
-    tagMap = await remoteGitTags(url)
+    tagMap = await tagsPromise
   }
   // catch a variety of errors that occur on invalid or private repos
   catch (e) {