Fix escaping of percent signs in the shell lexer

Of course, we do have cases where we want to escape the percent signs,
and our regexes were not fully correct for this case.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

lib/build/shell_example_lexer.py

@@ -46,12 +46,13 @@ class ShellExampleLexer(RegexLexer):
       # switch to state input on '$ ' at the start of the line
       (r"^\$ ", Text, "input"),
       (r"\s+", Text),
-      (r"[^#%\s]+", Text),
+      (r"[^#%\s\\]+", Text),
+      (r"\\", Text),
       ],
     "input": [
       include("comments"),
       include("userinput"),
-      (r"[^%\\\s]+", Generic.Strong),
+      (r"[^#%\s\\]+", Generic.Strong),
       (r"\\\n", Generic.Strong),
       (r"\\", Generic.Strong),
       # switch to prev state at non-escaped new-line
@@ -62,7 +63,7 @@ class ShellExampleLexer(RegexLexer):
       (r"#.*\n", Comment.Single),
       ],
     "userinput": [
-      (r"\\%", Text),
+      (r"(\\)(%)", bygroups(None, Text)),
       (r"(%)([^%]*)(%)", bygroups(None, Name.Variable, None)),
       ],
     }