Enter on a +/- diff line jumps to that line

This is useful particularly in conjunction with :Gblame.  Press `i` on a
line in a blame to open the commit.  If the diff reveals a new point of
interest, press enter on that line to jump to it in the history, then
:Gblame again.

plugin/fugitive.vim

@@ -2177,6 +2177,21 @@ function! s:GF(mode) abort
       elseif getline('.') =~# '^[+-]\{3\} [ab/]'
         let ref = getline('.')[4:]
 
+      elseif getline('.') =~# '^[+-]' && search('^@@ -\d\+,\d\+ +\d\+,','bnW')
+        let type = getline('.')[0]
+        let lnum = line('.') - 1
+        let offset = -1
+        while getline(lnum) !~# '^@@ -\d\+,\d\+ +\d\+,'
+          if getline(lnum) =~# '^[ '.type.']'
+            let offset += 1
+          endif
+          let lnum -= 1
+        endwhile
+        let offset += matchstr(getline(lnum), type.'\zs\d\+')
+        let ref = getline(search('^'.type.'\{3\} [ab]/','bnW'))[4:-1]
+        let dcmd = '+'.offset.'|foldopen'
+        let dref = ''
+
       elseif getline('.') =~# '^rename from '
         let ref = 'a/'.getline('.')[12:]
       elseif getline('.') =~# '^rename to '