grepo: get grepo projects as submodules in python

Summary:
Plug into exisiting python submodule infrastructure for grepo projects, since grepo project is a
similar concept that can benefit from implementations like `workingparentnode()`.

Once `parsesubmodules()` returns grepo submodules, the existing pipeline handles the rest:
`submodulestatus()` compares manifest nodes against working copy nodes, and `workingfilectx.data()`
generates `Subproject commit HASH` content.

Reviewed By: quark-zju

Differential Revision: D102908297

fbshipit-source-id: c738a0826b30588ae5114aee6a56bc143abdf207

Author: taidaii

eden/scm/sapling/git.py

@@ -884,6 +884,10 @@ def parsesubmodules(ctx):
         repo.ui.note(_("submodules are disabled via git.submodules\n"))
         return {}
     if ".gitmodules" not in ctx:
+        from . import grepo
+
+        if grepo.GREPO_REQUIREMENT in repo.requirements:
+            return grepo.getgreposubmodules(ctx, repo)
         return {}
 
     data = ctx[".gitmodules"].data()
@@ -1198,9 +1202,12 @@ def workingparentnode(self):
         repopath = self.parentrepo.wvfs.join(self.path)
         dotgit_path = os.path.join(repopath, ".git")
 
-        if DOTGIT_REQUIREMENT in self.parentrepo.requirements and os.path.exists(
-            dotgit_path
-        ):
+        from .grepo import GREPO_REQUIREMENT
+
+        if (
+            DOTGIT_REQUIREMENT in self.parentrepo.requirements
+            or GREPO_REQUIREMENT in self.parentrepo.requirements
+        ) and os.path.exists(dotgit_path):
             # dotgit repo, .git/sl not yet initialized.
             # read git HEAD directly.
             git = bindings.gitcompat.BareGit(dotgit_path, self.parentrepo.ui._rcfg)

eden/scm/sapling/grepo.py

@@ -12,5 +12,29 @@
     https://gerrit.googlesource.com/git-repo
 """
 
+import weakref
+from typing import List
+
+from .git import Submodule
+
 # Whether to be compatible with `.repo/`.
 GREPO_REQUIREMENT = "grepo"
+
+
+def getgreposubmodules(ctx, repo) -> List[Submodule]:
+    """Synthesize Submodule objects from the parent manifest for Grepo repos.
+
+    Conceptually, grepo projects are very similar to Git submodules. Rust tree
+    resolver synthesizes them into tree manifest as GitSubmodule (flag "m" in Python).
+    This method synthesizes them into Python Submodule objects to plug into
+    existing infrastructure.
+    """
+    parent = ctx.p1() if ctx.node() is None else ctx
+    mf = parent.manifest()
+    submodules = []
+    for path in mf:
+        if mf.flags(path) == "m":
+            submodules.append(
+                Submodule(path, "", path, True, weakref.proxy(repo)),
+            )
+    return submodules

eden/scm/tests/test-dotrepo.t

@@ -111,8 +111,12 @@ modified outer project is reported by status
 Diff shows subproject commit change for the outer project:
 
   $ sl diff
-  abort: Is a directory: $TESTTMP/repodir/vendor/a
-  [255]
+  diff -r * vendor/a (glob)
+  --- a/vendor/a	* (glob)
+  +++ b/vendor/a	* (glob)
+  @@ -1,1 +1,1 @@
+  -Subproject commit ac4ea71567e4779db728eebfc962382b53064bdb
+  +Subproject commit 8b78e5ec15214e009eb98624ee4dda34520d9720
 
 Modified nested (overlapping) project is reported by status:
 
@@ -127,8 +131,12 @@ Modified nested (overlapping) project is reported by status:
 Exact-path diff also works for the nested overlapping project:
 
   $ sl diff vendor/a/sub/c
-  abort: Is a directory: $TESTTMP/repodir/vendor/a/sub/c
-  [255]
+  diff -r * vendor/a/sub/c (glob)
+  --- a/vendor/a/sub/c	* (glob)
+  +++ b/vendor/a/sub/c	* (glob)
+  @@ -1,1 +1,1 @@
+  -Subproject commit 30c3ba4e8b4dced473cce4f5d10ced2eecbd2515
+  +Subproject commit 9f2c189e3840b5857f220136620130d40f5e71ce
 
 Modified non-overlapping project is reported by status:
 
@@ -144,5 +152,9 @@ Modified non-overlapping project is reported by status:
 Exact-path diff also works for the non-overlapping project:
 
   $ sl diff frameworks/b
-  abort: Is a directory: $TESTTMP/repodir/frameworks/b
-  [255]
+  diff -r * frameworks/b (glob)
+  --- a/frameworks/b	* (glob)
+  +++ b/frameworks/b	* (glob)
+  @@ -1,1 +1,1 @@
+  -Subproject commit 6a9d13442cc0deb7f2b531a00ac679f62d09edf3
+  +Subproject commit 96287d65976c48a2d3046495e3089baeb388a671