repos.BuildReporter: Option to ignore file dependencies

This turns out to be useful when may reports are
analized automatically.

repos_cmp/repos.py

@@ -435,12 +435,15 @@ def _is_build_kind(kind):
 
 class BuildReporter:
 
-    def __init__(self, from_repo, to_repo, ignore=(), prefer=(), caching=True):
+    def __init__(self, from_repo, to_repo,
+                 ignore=(), prefer=(),
+                 caching=True, ignore_file_deps=False):
         self.from_repo = from_repo
         self.to_repo = to_repo
         self.ignore = ignore
         self.prefer = prefer
         self._cache = {} if caching else None
+        self.ignore_file_deps = ignore_file_deps
         self._warned_on = set()
 
     def _warn(self, text, subject):
@@ -506,6 +509,10 @@ class BuildReporter:
             # skip some platform-specific stuff
             if any(x in dep.name for x in _SPECIAL_DEPS):
                 continue
+            # ignore file dependencies if we're asked to
+            if self.ignore_file_deps and not _is_build_kind(kind):
+                if dep.name.startswith(b'/'):
+                    continue
             # skip dependencies already present in to_repo
             if any(self.to_repo.providers(dep)):
                 continue