feat(git): Resolve more forms of commit reference

Specifically, we previously didn't resolve short commit hashes into the
full ones.

These functions provide a single place to later add more ways of
selection a commit, such as `HEAD~1`.

Author: AtkinsSJ

packages/git/src/git-helpers.js

@@ -17,6 +17,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 import path from 'path-browserify';
+import git from 'isomorphic-git';
 
 /**
  * Attempt to locate the git repository directory.
@@ -137,3 +138,43 @@ export const group_positional_arguments = (arg_tokens) => {
 
     return result;
 }
+
+/**
+ * Take some kind of reference, and resolve it to a full oid if possible.
+ * @param git_context Object of common parameters to isomorphic-git methods
+ * @param ref Reference to resolve
+ * @returns {Promise<string>} Full oid, or a thrown Error
+ */
+export const resolve_to_oid = async (git_context, ref) => {
+    const [ resolved_oid, expanded_oid ] = await Promise.allSettled([
+        git.resolveRef({ ...git_context, ref }),
+        git.expandOid({ ...git_context, oid: ref }),
+    ]);
+    let oid;
+    if (resolved_oid.status === 'fulfilled') {
+        oid = resolved_oid.value;
+    } else if (expanded_oid.status === 'fulfilled') {
+        oid = expanded_oid.value;
+    } else {
+        throw new Error(`Unable to resolve reference '${ref}'`);
+    }
+    // TODO: Advanced revision selection, see https://git-scm.com/book/en/v2/Git-Tools-Revision-Selection
+    //       and https://git-scm.com/docs/gitrevisions
+    return oid;
+}
+
+/**
+ * Similar to resolve_to_oid, but makes sure the oid refers to a commit.
+ * Returns the commit object because we had to retrieve it anyway.
+ * @param git_context Object of common parameters to isomorphic-git methods
+ * @param ref Reference to resolve
+ * @returns {Promise<ReadCommitResult>} ReadCommitResult object as returned by git.readCommit(), or a thrown Error
+ */
+export const resolve_to_commit = async (git_context, ref) => {
+    const resolved_oid = await resolve_to_oid(git_context, ref);
+    try {
+        return await git.readCommit({ ...git_context, oid: resolved_oid });
+    } catch (e) {
+        throw new Error(`bad revision '${ref}'`);
+    }
+}

packages/git/src/subcommands/checkout.js

@@ -17,7 +17,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 import git from 'isomorphic-git';
-import { find_repo_root, shorten_hash } from '../git-helpers.js';
+import { find_repo_root, resolve_to_commit, shorten_hash } from '../git-helpers.js';
 import { SHOW_USAGE } from '../help.js';
 
 const CHECKOUT = {
@@ -137,10 +137,11 @@ const CHECKOUT = {
                 return;
             }
 
-            const old_oid = await git.resolveRef({ fs, dir, gitdir, ref: 'HEAD' });
-
-            const oid = await git.resolveRef({ fs, dir, gitdir, ref: reference });
-            if (!oid)
+            const [ old_commit, commit ] = await Promise.all([
+                resolve_to_commit({ fs, dir, gitdir, cache }, 'HEAD'),
+                resolve_to_commit({ fs, dir, gitdir, cache }, reference ),
+            ]);
+            if (!commit)
                 throw new Error(`Reference '${reference}' not found.`);
 
             await git.checkout({
@@ -154,14 +155,11 @@ const CHECKOUT = {
             if (branches.includes(reference)) {
                 stdout(`Switched to branch '${reference}'`);
             } else {
-                const commit = await git.readCommit({ fs, dir, gitdir, oid });
                 const commit_title = commit.commit.message.split('\n', 2)[0];
-
-                const old_commit = await git.readCommit({ fs, dir, gitdir, oid: old_oid });
                 const old_commit_title = old_commit.commit.message.split('\n', 2)[0];
 
-                stdout(`Previous HEAD position was ${shorten_hash(old_oid)} ${old_commit_title}`);
-                stdout(`HEAD is now at ${shorten_hash(oid)} ${commit_title}`);
+                stdout(`Previous HEAD position was ${shorten_hash(old_commit.oid)} ${old_commit_title}`);
+                stdout(`HEAD is now at ${shorten_hash(commit.oid)} ${commit_title}`);
             }
         }
     }

packages/git/src/subcommands/diff.js

@@ -17,7 +17,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 import git, { STAGE, TREE, WORKDIR } from 'isomorphic-git';
-import { find_repo_root, group_positional_arguments } from '../git-helpers.js';
+import { find_repo_root, group_positional_arguments, resolve_to_commit, resolve_to_oid } from '../git-helpers.js';
 import { SHOW_USAGE } from '../help.js';
 import * as Diff from 'diff';
 import path from 'path-browserify';
@@ -123,13 +123,14 @@ export default {
         const { before: commit_args, after: path_args } = group_positional_arguments(tokens);
 
         // Ensure all commit_args are commit references
-        const resolved_commit_refs = await Promise.allSettled(commit_args.map(commit_arg => {
-            return git.resolveRef({ fs, dir, gitdir, ref: commit_arg });
+        const resolved_commits = await Promise.allSettled(commit_args.map(commit_arg => {
+            return resolve_to_commit({ fs, dir, gitdir, cache }, commit_arg);
         }));
-        for (const [i, ref] of resolved_commit_refs.entries()) {
-            if (ref.status === 'rejected')
+        for (const [i, commit] of resolved_commits.entries()) {
+            if (commit.status === 'rejected')
                 throw new Error(`bad revision '${commit_args[i]}'`);
         }
+        const [ from_oid, to_oid ] = resolved_commits.map(it => it.value.oid);
 
         const path_filters = path_args.map(it => path.resolve(env.PWD, it));
         const diff_ctx = {
@@ -153,7 +154,7 @@ export default {
             // Show staged changes
             diffs = await diff_git_trees({
                 ...diff_ctx,
-                a_tree: TREE({ ref: commit_args[0] ?? 'HEAD' }),
+                a_tree: TREE({ ref: from_oid ?? 'HEAD' }),
                 b_tree: STAGE(),
                 read_a: read_tree,
                 read_b: read_staged,
@@ -171,7 +172,7 @@ export default {
             // Changes from commit to workdir
             diffs = await diff_git_trees({
                 ...diff_ctx,
-                a_tree: TREE({ ref: commit_args[0] }),
+                a_tree: TREE({ ref: from_oid }),
                 b_tree: WORKDIR(),
                 read_a: read_tree,
                 read_b: read_tree,
@@ -180,8 +181,8 @@ export default {
             // Changes from one commit to another
             diffs = await diff_git_trees({
                 ...diff_ctx,
-                a_tree: TREE({ ref: commit_args[0] }),
-                b_tree: TREE({ ref: commit_args[1] }),
+                a_tree: TREE({ ref: from_oid }),
+                b_tree: TREE({ ref: to_oid }),
                 read_a: read_tree,
                 read_b: read_tree,
             });

packages/git/src/subcommands/push.js

@@ -18,7 +18,7 @@
  */
 import git from 'isomorphic-git';
 import http from 'isomorphic-git/http/web';
-import { determine_fetch_remote, find_repo_root, shorten_hash } from '../git-helpers.js';
+import { determine_fetch_remote, find_repo_root, resolve_to_oid, shorten_hash } from '../git-helpers.js';
 import { SHOW_USAGE } from '../help.js';
 import { authentication_options, Authenticator } from '../auth.js';
 import { color_options, process_color_options } from '../color.js';
@@ -209,7 +209,7 @@ export default {
             // TODO: Canonical git only pushes "new" branches to the remote when configured to do so, or with --set-upstream.
             //       So, we should show some kind of warning and stop, if that's not the case.
 
-            const source_oid = await git.resolveRef({ fs, dir, gitdir, ref: source });
+            const source_oid = await resolve_to_oid({ fs, dir, gitdir, cache }, source);
             const old_dest_oid = remote_ref?.oid;
 
             const is_up_to_date = source_oid === old_dest_oid;

packages/git/src/subcommands/show.js

@@ -17,7 +17,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 import git, { TREE } from 'isomorphic-git';
-import { find_repo_root } from '../git-helpers.js';
+import { find_repo_root, resolve_to_oid } from '../git-helpers.js';
 import {
     commit_formatting_options,
     diff_formatting_options,
@@ -108,12 +108,7 @@ export default {
 
         for (const ref of objects) {
             // Could be any ref, so first get the oid that's referred to.
-            const oid = await git.resolveRef({
-                fs,
-                dir,
-                gitdir,
-                ref,
-            });
+            const oid = await resolve_to_oid({ fs, dir, gitdir, cache }, ref);
 
             // Then obtain the object and parse it.
             const parsed_object = await git.readObject({