remote-helper: Accept revision for `patch.base`

When specifying a `patch.base` to point to for stacking patches, it's
useful to accept any kind of revspec, e.g. `HEAD^`.

Change the argument parsing to use the `Rev` type instead, and change
the `rad-patch-ahead-behind` to use `HEAD^` to test the example usage.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle-cli/examples/rad-patch-ahead-behind.md

@@ -123,7 +123,7 @@ If we want to instead create a "stacked" patch, we can do so with the
 `patch.base` push option:
 
 ``` (stderr)
-$ git push -o patch.message="Add Mel #2" -o patch.base=5c88a79d75f5c2b4cc51ee6f163d2db91ee198d7 rad HEAD:refs/patches
+$ git push -o patch.message="Add Mel #2" -o patch.base=HEAD^ rad HEAD:refs/patches
 ✓ Patch 11ab7fbec82c3aed393d7a696d6b3c7714735056 opened
 To rad://z42hL2jL4XNk6K8oHQaSWfMgCL7ji/z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi
  * [new reference]   HEAD -> refs/patches

radicle-remote-helper/src/lib.rs

@@ -13,6 +13,7 @@ use std::str::FromStr;
 use std::time;
 use std::{env, io};
 
+use radicle_cli::git::Rev;
 use thiserror::Error;
 
 use radicle::git;
@@ -25,6 +26,9 @@ use radicle_cli::terminal as cli;
 
 #[derive(Debug, Error)]
 pub enum Error {
+    /// Failed to parse `base`.
+    #[error("failed to parse base revision: {0}")]
+    Base(Box<dyn std::error::Error>),
     /// Remote repository not found (or empty).
     #[error("remote repository `{0}` not found")]
     RepositoryNotFound(PathBuf),
@@ -70,7 +74,7 @@ pub struct Options {
     /// Open patch in draft mode.
     draft: bool,
     /// Patch base to use, when opening or updating a patch.
-    base: Option<git::Oid>,
+    base: Option<Rev>,
     /// Patch message.
     message: cli::patch::Message,
 }
@@ -138,7 +142,8 @@ pub fn run(profile: radicle::Profile) -> Result<(), Error> {
                                     opts.message.append(val);
                                 }
                                 "patch.base" => {
-                                    let base = val.parse()?;
+                                    let base = cli::args::rev(&val.into())
+                                        .map_err(|e| Error::Base(e.into()))?;
                                     opts.base = Some(base);
                                 }
                                 _ => {

radicle-remote-helper/src/push.rs

@@ -309,7 +309,7 @@ fn patch_open<G: Signer>(
     let (_, target) = stored.canonical_head()?;
     let head = commit.id().into();
     let base = if let Some(base) = opts.base {
-        base
+        base.resolve(working)?
     } else {
         stored.merge_base(&target, &head)?
     };
@@ -425,7 +425,7 @@ fn patch_update<G: Signer>(
     let (_, target) = stored.canonical_head()?;
     let head: git::Oid = commit.id().into();
     let base = if let Some(base) = opts.base {
-        base
+        base.resolve(working)?
     } else {
         stored.merge_base(&target, &head)?
     };