Git - Add the ability to fetch a branch before it is checked out

extensions/git/package.json

@@ -2340,6 +2340,12 @@
           "default": false,
           "description": "%config.rebaseWhenSync%"
         },
+        "git.fetchBeforeCheckout": {
+          "type": "boolean",
+          "scope": "resource",
+          "default": false,
+          "description": "%config.fetchBeforeCheckout%"
+        },
         "git.fetchOnPull": {
           "type": "boolean",
           "scope": "resource",

extensions/git/package.nls.json

@@ -200,6 +200,7 @@
 	"config.rebaseWhenSync": "Force git to use rebase when running the sync command.",
 	"config.confirmEmptyCommits": "Always confirm the creation of empty commits for the 'Git: Commit Empty' command.",
 	"config.fetchOnPull": "When enabled, fetch all branches when pulling. Otherwise, fetch just the current one.",
+	"config.fetchBeforeCheckout": "Controls whether a branch that does not have outgoing commits is fast-forwarded before it is checked out.",
 	"config.pullTags": "Fetch all tags when pulling.",
 	"config.pruneOnFetch": "Prune when fetching.",
 	"config.autoStash": "Stash any changes before pulling and restore them after successful pull.",

extensions/git/src/api/git.d.ts

@@ -350,5 +350,6 @@ export const enum GitErrorCodes {
 	PatchDoesNotApply = 'PatchDoesNotApply',
 	NoPathFound = 'NoPathFound',
 	UnknownPath = 'UnknownPath',
-	EmptyCommitMessage = 'EmptyCommitMessage'
+	EmptyCommitMessage = 'EmptyCommitMessage',
+	BranchFastForwardRejected = 'BranchFastForwardRejected'
 }

extensions/git/src/commands.ts

@@ -33,13 +33,18 @@ class CheckoutItem implements QuickPickItem {
 	constructor(protected repository: Repository, protected ref: Ref) { }
 
 	async run(opts?: { detached?: boolean }): Promise<void> {
-		const ref = this.ref.name;
-
-		if (!ref) {
+		if (!this.ref.name) {
 			return;
 		}
 
-		await this.repository.checkout(ref, opts);
+		const config = workspace.getConfiguration('git', Uri.file(this.repository.root));
+		const fetchBeforeCheckout = config.get<boolean>('fetchBeforeCheckout', false) === true;
+
+		if (fetchBeforeCheckout) {
+			await this.repository.fastForwardBranch(this.ref.name!);
+		}
+
+		await this.repository.checkout(this.ref.name, opts);
 	}
 }
 
@@ -49,6 +54,14 @@ class CheckoutTagItem extends CheckoutItem {
 	override get description(): string {
 		return localize('tag at', "Tag at {0}", this.shortCommit);
 	}
+
+	override async run(opts?: { detached?: boolean }): Promise<void> {
+		if (!this.ref.name) {
+			return;
+		}
+
+		await this.repository.checkout(this.ref.name, opts);
+	}
 }
 
 class CheckoutRemoteHeadItem extends CheckoutItem {

extensions/git/src/git.ts

@@ -1708,6 +1708,9 @@ export class Repository {
 				err.gitErrorCode = GitErrorCodes.NoRemoteRepositorySpecified;
 			} else if (/Could not read from remote repository/.test(err.stderr || '')) {
 				err.gitErrorCode = GitErrorCodes.RemoteConnectionError;
+			} else if (/! \[rejected\].*\(non-fast-forward\)/m.test(err.stderr || '')) {
+				// The local branch has outgoing changes and it cannot be fast-forwarded.
+				err.gitErrorCode = GitErrorCodes.BranchFastForwardRejected;
 			}
 
 			throw err;

extensions/git/src/repository.ts

@@ -1363,6 +1363,27 @@ export class Repository implements Disposable {
 		await this.run(Operation.RenameBranch, () => this.repository.renameBranch(name));
 	}
 
+	@throttle
+	async fastForwardBranch(name: string): Promise<void> {
+		// Get branch details
+		const branch = await this.getBranch(name);
+		if (!branch.upstream?.remote || !branch.upstream?.name || !branch.name) {
+			return;
+		}
+
+		try {
+			// Fast-forward the branch if possible
+			const options = { remote: branch.upstream.remote, ref: `${branch.upstream.name}:${branch.name}` };
+			await this.run(Operation.Fetch, async () => this.repository.fetch(options));
+		} catch (err) {
+			if (err.gitErrorCode === GitErrorCodes.BranchFastForwardRejected) {
+				return;
+			}
+
+			throw err;
+		}
+	}
+
 	async cherryPick(commitHash: string): Promise<void> {
 		await this.run(Operation.CherryPick, () => this.repository.cherryPick(commitHash));
 	}