test: fix git configs for git 2.23 and above

Config values are now case-sensitive, so `commit.gpgsign=false` was
doing nothing.

PR-URL: #456
Credit: @isaacs
Close: #456
Reviewed-by: @claudiahdz

Author: isaacs

Diff for: lib/install/inflate-shrinkwrap.js

@@ -84,6 +84,7 @@ function tarballToVersion (name, tb) {
   } else {
     matchRegTarball = new RegExp(`^${registry}(.*)?/-/\\1-(.*)[.]tgz$`)
   }
+  if (!tb) return
   const match = tb.match(matchRegTarball)
   if (!match) return
   return match[2] || match[1]

Diff for: test/common-tap.js

@@ -193,7 +193,8 @@ exports.makeGitRepo = function (params, cb) {
     git.chainableExec(['config', 'user.name', user], opts),
     git.chainableExec(['config', 'user.email', email], opts),
     // don't time out tests waiting for a gpg passphrase or 2fa
-    git.chainableExec(['config', 'commit.gpgsign', 'false'], opts),
+    git.chainableExec(['config', 'commit.gpgSign', 'false'], opts),
+    git.chainableExec(['config', 'tag.gpgSign', 'false'], opts),
     git.chainableExec(['config', 'tag.forceSignAnnotated', 'false'], opts),
     git.chainableExec(['add'].concat(added), opts),
     git.chainableExec(['commit', '-m', message], opts)