try adding known extensions even if supplied filename has a dot

Author: davidcarlisle

required/graphics/graphics.dtx

@@ -1122,7 +1122,7 @@
     \ifx\filename@ext\relax
       \let\filename@ext\Gin@gzext
     \else
-      \edef\Gin@ext{\Gin@ext.\Gin@gzext}%
+      \edef\Gin@ext{\Gin@ext\Gin@sepdefault\Gin@gzext}%
     \fi
   \fi
   \ifx\filename@ext\relax
@@ -1133,6 +1133,34 @@
   \else
     \Gin@getbase{\Gin@sepdefault\filename@ext}%
 %    \end{macrocode}
+% At this point try adding an extension, even if the filename has one so
+% that \verb|a.b| may find \verb|a.b.png| if no file is found then revert
+% to the extension as given to get better error reporting.
+%
+% \changes{v1.3d}{2019/11/01}
+%     {Try adding an extension even if the filenam had a dot.}
+%    \begin{macrocode}
+\ifx\Gin@ext\relax
+\let\Gin@savedbase\filename@base
+\let\Gin@savedext\filename@ext
+  \edef\filename@base{\filename@base\Gin@sepdefault\filename@ext}%
+  \let\filename@ext\relax
+   \@for\Gin@temp:=\Gin@extensions\do{%
+      \ifx\Gin@ext\relax
+        \Gin@getbase\Gin@temp
+      \fi}%
+%    \end{macrocode}
+% Restore if no file found using theknown extensions.
+%    \begin{macrocode}
+  \ifx\Gin@ext\relax
+    \let\filename@base\Gin@savedbase
+    \let\filename@ext\Gin@savedext
+  \fi
+\fi
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%    \end{macrocode}
 % \changes{v0.4d}{1994/05/06}
 %     {Make file not found a warning not an error}
 % \changes{v0.6a}{1994/11/29}