(WIP) Improve support for selecting and downloading changes

This change adds support for selecting and downloading changes that
match a custom gerrit query (e.g. "is:open").

A new interactive function called gerrit-download-and-open-overview' was
added which downloads the change and opens an magit-commit buffer using
magit-show-commit'. (It the downloaded change is at the top of a
relation chain, the other commits are currently not displayed by this
`gerrit-download-and-open-overview' function.

Closes: #19
Change-Id: Ie3ed04a8f212cb8c0a98745d1dca4f680f420642

gerrit.el

@@ -1362,5 +1362,24 @@ workspace of the project."
 
      (call-interactively #'gerrit-upload-transient)))
 
+;; DONE split this up into two parts (one that downloads the change and one that opens the overview page sing magit-show-commit
+(defun gerrit-download-and-open-overview (changenr)
+  ;; since a simple "is:open" query might return a lot of gerrit-changes, it
+  ;; is possible to filter the returned results by setting an variable
+  ;; called `gerrit-interesting-open-changes-filter'.
+  (interactive (list
+                (let
+                    ((gerrit-change-singleline-columns '(number branch project subject)))
+                  (gerrit--select-change-from-matching-changes
+                   gerrit-interesting-open-changes-filter))))
+
+  (gerrit--init-accounts)
+  (gerrit-download:--in-known-repo changenr)
+  ;; TODO run magit-show-commit
+  ;; only when the above change is downloaded to avoid window-flickering
+  (magit-show-commit "HEAD"))
+
+
+
 (provide 'gerrit)
 ;;; gerrit.el ends here