Make git_fetch rule support writing the result to cache

Summary:
Writing these to cache has some benefits

1. reading from CAS is way faster (10x for the projects i tested)
2. allows cache hits, which means we may not need to materialize it at all

Reviewed By: rajneesh

Differential Revision: D69550163

fbshipit-source-id: dda00d4f7848d3dc0b889d63f27a637a89b2f6c7

prelude/decls/git_rules.bzl

@@ -25,6 +25,9 @@ git_fetch = prelude_rule(
     attrs = (
         # @unsorted-dict-items
         {
+            "allow_cache_upload": attrs.bool(doc = """
+                Whether the results of the fetch can be written to the action cache and CAS.
+            """, default = True),
             "repo": attrs.string(doc = """
                 Url suitable as a git remote.
             """),

prelude/git/git_fetch.bzl

@@ -39,6 +39,7 @@ def git_fetch_impl(ctx: AnalysisContext) -> list[Provider]:
         cmd,
         category = "git_fetch",
         local_only = True,
+        allow_cache_upload = ctx.attrs.allow_cache_upload,
     )
 
     return [DefaultInfo(default_output = work_tree)]