runtime: Tweak include key directive grammer in yaml merge processing.

docs/processing.rst

@@ -13,14 +13,16 @@ When a YAML configuration is loaded, will look for dictionary keys that match th
 
 and treat them as merge directives that update the dictionary by processing the directive and merging in its resolved value.
 
-Merge directives can have the following components:
+Merge keys can have the following components:
 
 .. productionlist::
      merge key      : merge_directive | merge_anchor | merge_strategy
-     merge_directive : "+"["?"]["include"][alias][relative_path][absolute_path]
+     merge_directive : "+"["?"][include][alias][relative_path][absolute_path]
+     include        : "include"[ALPHNUM]*
      alias          : "*"[PCHAR]*[PCHAR except "."]
      relative_path  : "."+
      absolute_path  : ["/" PCHAR*]+
+     ALPHNUM        : a-z, A-Z, 0-9, _, -
      PCHAR          : any printable character except "/"
      merge_anchor   : "+&"
      merge_strategy : "+%"
@@ -30,7 +32,7 @@ Each of these components are optional but at least one needs to be present, othe
 
 A leading '?' indicates that reference maybe missing, otherwise the processing will abort with an error.
 
-``include`` indicates that value of the merge key includes a yaml or json file to load.
+``include`` indicates that value of the merge key includes a yaml or json file to load. Can have optional trailing alphanumeric characters to ensure key is unique.
 
 ``*alias``: a reference to merge anchor that appears in either the current document or, a file was specified, from that file.
 

unfurl/merge.py

@@ -390,16 +390,17 @@ def __repr__(self):
         return self.key.key
 
 
-RE_FIRST = re.compile(r"([?]?)(include\d*)?([*]\S+)?([.]+$)?")
+RE_FIRST = re.compile(r"([?]?)(include[\w-]*)?([*]\S+)?([.]+$)?")
 
 MergeKey = namedtuple("MergeKey", "key, maybe, include, anchor, relative, pointer")
 
 
 def parse_merge_key(key: str) -> Optional[MergeKey]:
-    """
+    r"""
     +[maybe]?[include]?[anchor]?[relative]?[jsonpointer]?
 
-    [include] = "include"[number?]
+    [maybe] = "?"
+    [include] = "include"[\w-]*
     [anchor] = "*"[anchorname]
     relative = '.'+
     """