Add a setting that prevents fetch unless needed for new branch (#5449)

Fixes #5439

package.json

@@ -320,6 +320,11 @@
 					],
 					"description": "%githubPullRequests.pullBranch.description%"
 				},
+				"githubPullRequests.allowFetch": {
+					"type": "boolean",
+					"default": true,
+					"description": "%githubPullRequests.allowFetch.description%"
+				},
 				"githubPullRequests.ignoredPullRequestBranches": {
 					"type": "array",
 					"default": [],

package.nls.json

@@ -59,6 +59,7 @@
 	"githubPullRequests.pullBranch.prompt": "Prompt to pull a PR branch when changes are detected in the PR.",
 	"githubPullRequests.pullBranch.never": "Never pull a PR branch when changes are detected in the PR.",
 	"githubPullRequests.pullBranch.always": "Always pull a PR branch when changes are detected in the PR. When `\"git.autoStash\": true` this will instead `prompt` to prevent unexpected file changes.",
+	"githubPullRequests.allowFetch.description": "Allows `git fetch` to be run for checked-out pull request branches when checking for updates to the pull request.",
 	"githubPullRequests.ignoredPullRequestBranches.description": "Prevents branches that are associated with a pull request from being automatically detected. This will prevent review mode from being entered on these branches.",
 	"githubPullRequests.ignoredPullRequestBranches.items": "Branch name",
 	"githubPullRequests.neverIgnoreDefaultBranch.description": "Never offer to ignore a pull request associated with the default branch of a repository.",

src/common/settingKeys.ts

@@ -47,6 +47,7 @@ export const ISSUE_COMPLETION_FORMAT_SCM = 'issueCompletionFormatScm';
 export const CREATE_ISSUE_TRIGGERS = 'createIssueTriggers';
 export const DEFAULT = 'default';
 export const IGNORE_MILESTONES = 'ignoreMilestones';
+export const ALLOW_FETCH = 'allowFetch';
 
 // git
 export const GIT = 'git';

src/github/folderRepositoryManager.ts

@@ -14,6 +14,7 @@ import Logger from '../common/logger';
 import { Protocol, ProtocolType } from '../common/protocol';
 import { GitHubRemote, parseRemote, parseRepositoryRemotes, Remote } from '../common/remote';
 import {
+	ALLOW_FETCH,
 	AUTO_STASH,
 	DEFAULT_MERGE_METHOD,
 	GIT,
@@ -2219,7 +2220,7 @@ export class FolderRepositoryManager implements vscode.Disposable {
 			const remoteBranch = branch.upstream ? branch.upstream.name : branch.name;
 			if (remote) {
 				try {
-					if (shouldFetch) {
+					if (shouldFetch && vscode.workspace.getConfiguration(PR_SETTINGS_NAMESPACE).get<boolean>(ALLOW_FETCH, true)) {
 						await this._repository.fetch(remote, remoteBranch);
 					}
 				} catch (e) {