Better HTTP redirect detection

These HTTP headers may have other :GBrowse applications, so if we're
parsing them, we may as well hang onto them.

autoload/fugitive.vim

@@ -918,6 +918,8 @@ function! fugitive#RevParse(rev, ...) abort
   throw 'fugitive: failed to parse revision ' . a:rev
 endfunction
 
+" Section: Git config
+
 function! s:ConfigTimestamps(dir, dict) abort
   let files = ['/etc/gitconfig', '~/.gitconfig',
         \ len($XDG_CONFIG_HOME) ? $XDG_CONFIG_HOME . '/git/config' : '~/.config/git/config']
@@ -1168,7 +1170,39 @@ function! fugitive#SshHostAlias(authority) abort
   return (len(user) ? user . '@' : '') . get(c, 'hostname', host) . (port =~# '^\%(22\)\=$' ? '' : ':' . port)
 endfunction
 
-let s:redirects = {}
+function! s:CurlResponse(result) abort
+  let a:result.headers = {}
+  for line in a:result.exit_status ? [] : remove(a:result, 'stdout')
+    let header = matchlist(line, '^\([[:alnum:]-]\+\):\s\(.\{-\}\)'. "\r\\=$")
+    if len(header)
+      let k = tolower(header[1])
+      if has_key(a:result.headers, k)
+        let a:result.headers[k] .= ', ' . header[2]
+      else
+        let a:result.headers[k] = header[2]
+      endif
+    elseif empty(line)
+      break
+    endif
+  endfor
+endfunction
+
+let s:remote_headers = {}
+
+function! fugitive#RemoteHttpHeaders(remote) abort
+  if a:remote !~# '^https\=://.' || !s:executable('curl')
+    return {}
+  endif
+  if !has_key(s:remote_headers, a:remote)
+    let url = a:remote . '/info/refs?service=git-upload-pack'
+    let exec = s:JobExecute(
+          \ ['curl', '--disable', '--silent', '--max-time', '5', '-X', 'GET', '-I',
+          \ url], {}, [function('s:CurlResponse')], {})
+    call fugitive#Wait(exec)
+    let s:remote_headers[a:remote] = exec.headers
+  endif
+  return s:remote_headers[a:remote]
+endfunction
 
 function! fugitive#ResolveRemote(remote) abort
   let scp_authority = matchstr(a:remote, '^[^:/]\+\ze:\%(//\)\@!')
@@ -1182,15 +1216,11 @@ function! fugitive#ResolveRemote(remote) abort
     elseif authority !~# ':'
       return authority . ':' . path
     endif
-  elseif a:remote =~# '^https\=://' && s:executable('curl')
+  elseif a:remote =~# '^https\=://'
-    if !has_key(s:redirects, a:remote)
+    let headers = fugitive#RemoteHttpHeaders(a:remote)
-      let s:redirects[a:remote] = matchstr(join(s:JobExecute(
+    let loc = matchstr(get(headers, 'location', ''), '^https\=://.\{-\}\ze/info/refs?')
-            \ ['curl', '--disable', '--silent', '--max-time', '5', '-I',
+    if len(loc)
-            \ a:remote . '/info/refs?service=git-upload-pack'], {}, [], {}).stdout, "\n"),
+      return loc
-            \ 'Location: \zs\S\+\ze/info/refs?')
-    endif
-    if len(s:redirects[a:remote])
-      return s:redirects[a:remote]
     endif
   elseif a:remote =~# '^ssh://'
     let authority = matchstr(a:remote, '[^/?#]*', 6)
@@ -7125,7 +7155,11 @@ function! fugitive#BrowseCommand(line1, count, range, bang, mods, arg, args) abo
     if empty(remote) || remote ==# '.'
       let remote = s:Remote(dir)
     endif
-    let remote_url = fugitive#RemoteUrl(remote, dir)
+    if remote =~# ':'
+      let remote_url = remote
+    else
+      let remote_url = fugitive#RemoteUrl(remote, dir)
+    endif
     let raw = empty(remote_url) ? remote : remote_url
     let git_dir = s:GitDir(dir)