Overhaul :Gbrowse remote handling

plugin/fugitive.vim

@@ -2176,11 +2176,18 @@ endfunction
 
 " Section: Gbrowse
 
-call s:command("-bar -bang -range -nargs=* -complete=customlist,s:EditComplete Gbrowse :execute s:Browse(<bang>0,<line1>,<count>,<f-args>)")
+call s:command("-bar -bang -range=0 -nargs=* -complete=customlist,s:EditComplete Gbrowse :execute s:Browse(<bang>0,<line1>,<count>,<f-args>)")
 
 function! s:Browse(bang,line1,count,...) abort
   try
-    let rev = a:0 ? substitute(join(a:000, ' '),'@[[:alnum:]_-]\w\+\%(://.\{-\}\)\=$','','') : ''
+    let validremote = '\.\|\.\=/.*\|[[:alnum:]_-]\+\%(://.\{-\}\)'
+    if a:0
+      let remote = matchstr(join(a:000, ' '),'@\zs\%('.validremote.'\)$')
+      let rev = substitute(join(a:000, ' '),'@\%('.validremote.'\)$','','')
+    else
+      let remote = ''
+      let rev = ''
+    endif
     if rev ==# ''
       let expanded = s:buffer().rev()
     elseif rev ==# ':'
@@ -2195,6 +2202,7 @@ function! s:Browse(bang,line1,count,...) abort
       let path = matchstr(full,'://.*//\w\+\zs/.*')
       if commit =~ '..'
         let type = s:repo().git_chomp('cat-file','-t',commit.s:sub(path,'^/',':'))
+        let branch = matchstr(expanded, '^[^:]*')
       else
         let type = 'blob'
       endif
@@ -2215,9 +2223,6 @@ function! s:Browse(bang,line1,count,...) abort
     if type ==# 'tree' && !empty(path)
       let path = s:sub(path, '/\=$', '/')
     endif
-    if empty(commit) && path !~# '^\.git/'
-      let commit = s:repo().rev_parse('HEAD')
-    endif
     if path =~# '^\.git/.*HEAD' && filereadable(s:repo().dir(path[5:-1]))
       let body = readfile(s:repo().dir(path[5:-1]))[0]
       if body =~# '^\x\{40\}$'
@@ -2229,35 +2234,54 @@ function! s:Browse(bang,line1,count,...) abort
       endif
     endif
 
-    if a:0 && join(a:000, ' ') =~# '@[[:alnum:]_-]\+\%(://.\{-\}\)\=$'
-      let remote = matchstr(join(a:000, ' '),'@\zs[[:alnum:]_-]\+\%(://.\{-\}\)\=$')
-    elseif path =~# '^\.git/refs/remotes/.'
-      let remote = matchstr(path,'^\.git/refs/remotes/\zs[^/]\+')
-    else
-      let remote = 'origin'
-      let branch = matchstr(rev,'^[[:alnum:]/._-]\+\ze[:^~@]')
-      if branch ==# '' && path =~# '^\.git/refs/\w\+/'
-        let branch = s:sub(path,'^\.git/refs/\w+/','')
+    let merge = ''
+    if path =~# '^\.git/refs/remotes/.'
+      if empty(remote)
+        let remote = matchstr(path, '^\.git/refs/remotes/\zs[^/]\+')
       endif
-      if filereadable(s:repo().dir('refs/remotes/'.branch))
-        let remote = matchstr(branch,'[^/]\+')
-        let rev = rev[strlen(remote)+1:-1]
-      else
-        if branch ==# ''
-          let branch = matchstr(s:repo().head_ref(),'\<refs/heads/\zs.*')
+      let merge = matchstr(path, '^\.git/refs/remotes/[^/]\+/\zs.\+')
+      let branch = ''
+      let path = '.git/refs/heads/'.merge
+    elseif path =~# '^\.git/refs/heads/.'
+      let branch = path[16:-1]
+    elseif !exists('branch')
+      let branch = s:repo().head()
+    endif
+    if !empty(branch)
+      let r = s:repo().git_chomp('config','branch.'.branch.'.remote')
+      let m = s:repo().git_chomp('config','branch.'.branch.'.merge')[11:-1]
+      if r ==# '.' && !empty(m)
+        let r2 = s:repo().git_chomp('config','branch.'.m.'.remote')
+        if r2 !~# '^\.\=$'
+          let r = r2
+          let m = s:repo().git_chomp('config','branch.'.m.'.merge')[11:-1]
         endif
-        if branch != ''
-          let remote = s:repo().git_chomp('config','branch.'.branch.'.remote')
-          if remote =~# '^\.\=$'
-            let remote = 'origin'
-          elseif rev[0:strlen(branch)-1] ==# branch && rev[strlen(branch)] =~# '[:^~@]'
-            let rev = s:repo().git_chomp('config','branch.'.branch.'.merge')[11:-1] . rev[strlen(branch):-1]
-          endif
+      endif
+      if empty(remote)
+        let remote = r
+      endif
+      if r ==# '.' || r ==# remote
+        let merge = m
+        if path =~# '^\.git/refs/heads/.'
+          let path = '.git/refs/heads/'.merge
         endif
       endif
     endif
 
-    let raw = s:repo().git_chomp('config','remote.'.remote.'.url')
+    if empty(commit) && path !~# '^\.git/'
+      if a:line1 && !a:count && !empty(merge)
+        let commit = merge
+      else
+        let commit = s:repo().rev_parse('HEAD')
+      endif
+    endif
+
+    if empty(remote)
+      let remote = '.'
+      let raw = s:repo().git_chomp('config','remote.origin.url')
+    else
+      let raw = s:repo().git_chomp('config','remote.'.remote.'.url')
+    endif
     if raw ==# ''
       let raw = remote
     endif
@@ -2266,7 +2290,7 @@ function! s:Browse(bang,line1,count,...) abort
       let url = call(Handler, [{
             \ 'repo': s:repo(),
             \ 'remote': raw,
-            \ 'revision': rev,
+            \ 'revision': 'No longer provided',
             \ 'commit': commit,
             \ 'path': path,
             \ 'type': type,
@@ -2277,8 +2301,10 @@ function! s:Browse(bang,line1,count,...) abort
       endif
     endfor
 
-    if empty(url)
-      call s:throw("Instaweb failed to start and '".remote."' is not a supported remote")
+    if empty(url) && raw ==# '.'
+      call s:throw("Instaweb failed to start")
+    elseif empty(url)
+      call s:throw('"'.remote."' is not a supported remote")
     endif
 
     let url = s:gsub(url, '[ <>]', '\="%".printf("%02X",char2nr(submatch(0)))')
@@ -2360,6 +2386,9 @@ function! s:github_url(opts, ...) abort
 endfunction
 
 function! s:instaweb_url(opts) abort
+  if a:opts.remote !=# '.'
+    return ''
+  endif
   let output = a:opts.repo.git_chomp('instaweb','-b','unknown')
   if output =~# 'http://'
     let root = matchstr(output,'http://.*').'/?p='.fnamemodify(a:opts.repo.dir(),':t')