types: support multi-format deserialization for HgId

Summary:
Switch from the default tuple deserialization which only understands the tuple
format, to "bytes" deserialization, which understands not only the existing
"tuple" format (therefore compatible with old data), but also "bytes" and "hex"
formats (for CBOR).

This will unblock us from switching to bytes serialization in the future.

Note: This is a breaking change for mincode serialization. Mincode + HgId users
(zsotre, metalog) have switched to explicit tuple serialization so they don't use
the default deserializaiton and remain unaffected.

Reviewed By: kulshrax

Differential Revision: D23966995

fbshipit-source-id: 83dd53f57bd4e6098de054f46a1d47f8b48133d0

eden/scm/lib/types/src/hgid.rs

@@ -12,7 +12,7 @@ use std::{
 };
 
 use anyhow::Result;
-use serde_derive::{Deserialize, Serialize};
+use serde::{de::Deserializer, Deserialize, Serialize};
 use thiserror::Error;
 
 use crate::parents::Parents;
@@ -70,19 +70,15 @@ struct HgIdError(String);
 ///
 /// [1]: Depends on actual data of `HgId`.
 /// [2]: JSON only supports utf-8 data.
-#[derive(
-    Clone,
-    Copy,
-    Eq,
-    Hash,
-    Ord,
-    PartialEq,
-    PartialOrd,
-    Serialize,
-    Deserialize
-)]
+#[derive(Clone, Copy, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
 pub struct HgId([u8; HgId::len()]);
 
+impl<'de> Deserialize<'de> for HgId {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        crate::serde_with::hgid::bytes::deserialize(deserializer)
+    }
+}
+
 /// The nullid (0x00) is used throughout Mercurial to represent "None".
 /// (For example, a commit will have a nullid p2, if it has no second parent).
 pub const NULL_ID: HgId = HgId([0; HgId::len()]);