Add GitHub PR comparison command

README.md

@@ -12,6 +12,8 @@ In bigger projects with many files it also provides **context**, it gives you a
 
 - Working tree comparison against any chosen branch, tag, or commit
 
+- Compare GitHub Pull Requests
+
 - Switch between tree and list view
 
 - Compare in merge or full mode
@@ -34,6 +36,22 @@ By default, the tree view is located in its own container accessible from the ac
 
 <img src="screenshots/move-view.gif" alt="Moving of Git Tree Compare view between containers" width="256" />
 
+## Compare GitHub Pull Requests
+
+You can quickly view GitHub PR changes directly in VS Code using the **Compare GitHub Pull Request** command:
+
+1. Click the "..." menu button in the Git Tree Compare view title bar
+2. Select **Compare GitHub Pull Request...**
+3. Enter the GitHub PR URL (e.g., `https://github.com/owner/repo/pull/123`)
+4. Authenticate with GitHub if prompted (uses VS Code's built-in GitHub authentication)
+5. The extension will:
+   - Fetch the PR's head commit
+   - Checkout the PR branch as `pr/<number>/<headOwner>/<headRefName>`
+   - Compare it against the PR's base branch
+   - Display all changes in the tree view
+
+This feature works with both PRs from the same repository and PRs from forks.
+
 ## Settings
 
 `gitTreeCompare.diffMode` Determines how the comparison is performed, either by computing a merge base commit first and then comparing against that (equivalent to pull request diffs, default), or by comparing directly to the given base (useful to see the exact diff).

package.json

@@ -164,6 +164,12 @@
                 "title": "Copy Relative Path",
                 "category": "Git Tree Compare"
             },
+            {
+                "command": "gitTreeCompare.compareGitHubPullRequest",
+                "title": "Compare GitHub Pull Request...",
+                "icon": "$(github)",
+                "category": "Git Tree Compare"
+            },
             {
                 "command": "gitTreeCompare.sortByName",
                 "title": "Sort by Name",
@@ -247,6 +253,11 @@
                     "when": "view == gitTreeCompare",
                     "group": "1_state"
                 },
+                {
+                    "command": "gitTreeCompare.compareGitHubPullRequest",
+                    "when": "view == gitTreeCompare",
+                    "group": "1_state"
+                },
                 {
                     "command": "gitTreeCompare.openAllChanges",
                     "when": "view == gitTreeCompare",
@@ -582,6 +593,7 @@
         "webpack-cli": "^4.2.0"
     },
     "dependencies": {
+        "@octokit/rest": "^22.0.1",
         "@vscode/iconv-lite-umd": "0.7.0",
         "byline": "^5.0.0",
         "file-type": "^7.2.0",

src/extension.ts

@@ -60,6 +60,11 @@ export function activate(context: ExtensionContext) {
             provider!.promptChangeBase();
         });
     });
+    commands.registerCommand(NAMESPACE + '.compareGitHubPullRequest', () => {
+        runAfterInit(() => {
+            provider!.compareGitHubPullRequest();
+        });
+    });
     commands.registerCommand(NAMESPACE + '.refresh', () => {
         runAfterInit(() => {
             provider!.manualRefresh();

src/gitHelper.ts

@@ -237,8 +237,13 @@ export async function diffIndex(repo: Repository, ref: string, refreshIndex: boo
     return statuses;
 }
 
-export async function hasUncommittedChanges(repo: Repository, path: string): Promise<boolean> {
-    const result = await repo.exec(['status', '-z', path]);
+export async function hasUncommittedChanges(repo: Repository, path: string, ignoreUntracked: boolean = false): Promise<boolean> {
+    const args = ['status', '-z'];
+    if (ignoreUntracked) {
+        args.push('-uno');
+    }
+    args.push(path);
+    const result = await repo.exec(args);
     return result.stdout.trim() !== '';
 }
 

src/treeProvider.ts

@@ -5,7 +5,7 @@ import * as fs from 'fs'
 import { TreeDataProvider, TreeItem, TreeItemCollapsibleState,
          Uri, Disposable, EventEmitter, TextDocumentShowOptions,
          QuickPickItem, ProgressLocation, Memento, OutputChannel,
-         workspace, commands, window, env, WorkspaceFoldersChangeEvent, TreeView, ThemeIcon, TreeItemCheckboxState, TreeCheckboxChangeEvent } from 'vscode'
+         workspace, commands, window, env, WorkspaceFoldersChangeEvent, TreeView, ThemeIcon, TreeItemCheckboxState, TreeCheckboxChangeEvent, authentication } from 'vscode'
 import { NAMESPACE } from './constants'
 import { Repository, Git } from './git/git'
 import { Ref, RefType } from './git/api/git'
@@ -16,6 +16,8 @@ import { getDefaultBranch, getHeadModificationDate, getBranchCommit,
 import { debounce, throttle } from './git/decorators'
 import { normalizePath } from './fsUtils';
 import { API as GitAPI, Repository as GitAPIRepository } from './typings/git';
+import { Octokit } from '@octokit/rest';
+
 
 type SortOrder = 'name' | 'path' | 'status' | 'recentlyModified';
 
@@ -1254,6 +1256,193 @@ export class GitTreeCompareProvider implements TreeDataProvider<Element>, Dispos
         });
     }
 
+    async compareGitHubPullRequest() {
+        if (!this.repository) {
+            window.showErrorMessage('No repository selected');
+            return;
+        }
+
+        const repository = this.repository;
+
+        // Check for uncommitted changes (ignoring untracked files)
+        try {
+            if (await hasUncommittedChanges(repository, repository.root, true)) {
+                window.showErrorMessage(
+                    'Please commit your changes or stash them before continuing.',
+                    { modal: true }
+                );
+                    return;
+            }
+        } catch (e: any) {
+            this.log('Error checking for uncommitted changes', e);
+            // Continue anyway
+        }
+
+        // Prompt for PR URL
+        const prUrl = await window.showInputBox({
+            prompt: 'Enter GitHub Pull Request URL',
+            placeHolder: 'https://github.com/owner/repo/pull/123',
+            validateInput: (value: string) => {
+                const match = value.match(/github\.com\/([^\/]+)\/([^\/]+)\/pull\/(\d+)/);
+                if (!match) {
+                    return 'Invalid GitHub PR URL. Expected format: https://github.com/owner/repo/pull/123';
+                }
+                return null;
+            }
+        });
+
+        if (!prUrl) {
+            return;
+        }
+
+        // Parse the PR URL
+        const match = prUrl.match(/github\.com\/([^\/]+)\/([^\/]+)\/pull\/(\d+)/);
+        if (!match) {
+            window.showErrorMessage('Invalid GitHub PR URL format');
+            return;
+        }
+
+        const [, owner, repo, prNumberStr] = match;
+        const prNumber = parseInt(prNumberStr, 10);
+
+        await window.withProgress({
+            location: ProgressLocation.Notification,
+            title: `Fetching PR #${prNumber} from ${owner}/${repo}`,
+            cancellable: false
+        }, async () => {
+            try {
+                // Authenticate with GitHub
+                const session = await authentication.getSession('github', ['repo'], { createIfNone: true });
+                const octokit = new Octokit({ auth: session.accessToken });
+
+                // Fetch PR details
+                this.log(`Fetching PR details for ${owner}/${repo}#${prNumber}`);
+                const { data: pr } = await octokit.pulls.get({
+                    owner,
+                    repo,
+                    pull_number: prNumber
+                });
+
+                // Extract base and head information
+                const baseRef = pr.base.ref;
+                const headRef = pr.head.ref;
+                const headSha = pr.head.sha;
+
+                this.log(`PR #${prNumber}: base=${baseRef}, head=${headRef}, sha=${headSha}`);
+
+                // Fetch the PR branch if it's from a fork
+                const headRepo = pr.head.repo;
+                if (!headRepo) {
+                    window.showErrorMessage('Cannot access PR head repository. It may have been deleted.');
+                    return;
+                }
+
+                const headRepoUrl = headRepo.clone_url;
+                const isFork = headRepo.full_name !== pr.base.repo.full_name;
+
+                // Extract head owner for branch naming
+                const headOwner = pr.head.user?.login || pr.head.repo?.owner.login;
+                if (!headOwner) {
+                    window.showErrorMessage('Could not determine PR head owner.');
+                    return;
+                }
+
+                // Create a local branch name for the PR with owner and ref name
+                const localBranchName = `pr/${prNumber}/${headOwner}/${headRef}`;
+
+                // Fetch and create/update local branch for the PR
+                try {
+                    if (isFork) {
+                        // For forks, add a remote with pr-fork- prefix
+                        const forkRemoteName = `pr-fork-${headOwner}`;
+
+                        this.log(`Fetching PR #${prNumber} from fork owned by ${headOwner}: ${headRepoUrl}`);
+
+                        // Check if remote already exists, if not add it
+                        try {
+                            const existingUrl = (await repository.exec(['remote', 'get-url', forkRemoteName])).stdout.trim();
+                            // Update URL if it's different
+                            if (existingUrl !== headRepoUrl) {
+                                await repository.exec(['remote', 'set-url', forkRemoteName, headRepoUrl]);
+                                this.log(`Updated remote ${forkRemoteName} URL to ${headRepoUrl}`);
+                            }
+                        } catch {
+                            await repository.exec(['remote', 'add', forkRemoteName, headRepoUrl]);
+                            this.log(`Added remote ${forkRemoteName}`);
+                        }
+
+                        // Fetch the head ref from the fork
+                        await repository.fetch({ remote: forkRemoteName, ref: headRef });
+
+                        // Create/update local branch pointing to the fetched commit
+                        try {
+                            // Try to create new branch
+                            await repository.exec(['branch', localBranchName, headSha]);
+                        } catch {
+                            // Branch exists, force update it
+                            await repository.exec(['branch', '-f', localBranchName, headSha]);
+                        }
+
+                        // Set upstream to the fork remote
+                        await repository.exec(['branch', '--set-upstream-to', `${forkRemoteName}/${headRef}`, localBranchName]);
+
+                        this.log(`Created local branch ${localBranchName} tracking ${forkRemoteName}/${headRef}`);
+                    } else {
+                        // For same repo, use GitHub's pull/<id>/head refspec
+                        this.log(`Fetching PR #${prNumber} from origin`);
+                        await repository.exec(['fetch', 'origin', `pull/${prNumber}/head:${localBranchName}`]);
+
+                        // Set upstream to origin/<headRef> if the branch exists there
+                        try {
+                            // Fetch the actual head ref to update the remote tracking branch
+                            await repository.fetch({ remote: 'origin', ref: headRef });
+                            await repository.exec(['branch', '--set-upstream-to', `origin/${headRef}`, localBranchName]);
+                            this.log(`Created local branch ${localBranchName} tracking origin/${headRef}`);
+                        } catch {
+                            this.log(`Created local branch ${localBranchName} (no upstream - origin/${headRef} not found)`);
+                        }
+                    }
+                } catch (e: any) {
+                    let msg = 'Failed to fetch and create PR branch';
+                    this.log(msg, e);
+                    window.showErrorMessage(`${msg}: ${e.message}`);
+                    return;
+                }
+
+                // Checkout the local PR branch
+                try {
+                    this.log(`Checking out branch: ${localBranchName}`);
+                    await repository.checkout(localBranchName, []);
+                } catch (e: any) {
+                    let msg = 'Failed to checkout PR branch';
+                    this.log(msg, e);
+                    window.showErrorMessage(`${msg}: ${e.message}`);
+                    return;
+                }
+
+                // Update the comparison base to the PR base branch (use origin/* to avoid stale refs)
+                try {
+                    const originBaseRef = `origin/${baseRef}`;
+                    this.log(`Updating base to: ${originBaseRef}`);
+                    await this.updateRefs(originBaseRef);
+                    await this.updateDiff(false);
+                    this.log('Refreshing tree');
+                    this._onDidChangeTreeData.fire();
+                    window.showInformationMessage(`Now comparing PR #${prNumber}: ${pr.title}`);
+                } catch (e: any) {
+                    let msg = 'Failed to update comparison base';
+                    this.log(msg, e);
+                    window.showErrorMessage(`${msg}: ${e.message}`);
+                    return;
+                }
+            } catch (e: any) {
+                let msg = 'Failed to fetch GitHub PR';
+                this.log(msg, e);
+                window.showErrorMessage(`${msg}: ${e.message || e}`);
+            }
+        });
+    }
+
     async manualRefresh() {
         window.withProgress({ location: ProgressLocation.Window, title: 'Updating Tree' }, async _ => {
             try {