fix failure on fork PRs

lib/checkout.js

@@ -106,8 +106,10 @@ async function cloneLocalAndCheckout(from, to, branch) {
     debug(`local cloning ${gitRoot} into ${to}`);
     await Git().clone(gitRoot, to, { '--local'  : true });
 
-    debug(`checking out '${branch}'...`);
-    await Git(to).checkout(branch);
+    if (branch) {
+        debug(`checking out '${branch}'...`);
+        await Git(to).checkout(branch);
+    }
 }
 
 async function gitCheckoutBeforeAndAfter(gitDir, beforeBranch, afterBranch) {
@@ -131,32 +133,33 @@ async function gitCheckoutBeforeAndAfter(gitDir, beforeBranch, afterBranch) {
     const tempDir = tmp.dirSync({unsafeCleanup: true}).name;
     debug(`temporary directory: ${tempDir}`);
 
+    // before checkout --------------------------------------------------------------
+
     const beforeDir = path.join(tempDir, "before");
 
     // we can use the faster local clone only if the "branch" is present locally
     if (await hasBranch(gitDir, beforeBranch)) {
+        debug(`[before] using local cloning because existing checkout already has before branch '${beforeBranch}'`);
         await cloneLocalAndCheckout(gitDir, beforeDir, beforeBranch);
     } else {
+        debug(`[before] using remote cloning, as existing checkout does not have before branch '${beforeBranch}'`);
         // ...otherwise need to do a full remote clone
         await cloneRemoteAndCheckout(gitDir, beforeDir, beforeBranch);
     }
 
+    // after checkout --------------------------------------------------------------
+
     const afterDir = path.join(tempDir, "after");
 
-    // we can use the faster local clone only if the "branch" is present locally
-    if (await hasBranch(gitDir, afterBranch)) {
-        await cloneLocalAndCheckout(gitDir, afterDir, afterBranch);
-
-        try {
-            // need to ensure before branch is available under local name
-            await Git(afterDir).branch([beforeBranch, "-t", `origin/${beforeBranch}`]);
-        } catch (e) {
-            debug("ignoring error", e);
-        }
-    } else {
-        // ...otherwise need to do a full remote clone
-        await cloneRemoteAndCheckout(gitDir, afterDir, afterBranch);
+    debug(`[after] using local cloning`);
+    await cloneLocalAndCheckout(gitDir, afterDir);
+    try {
+        // need to ensure before branch is available under local name
+        await Git(afterDir).branch([beforeBranch, "-t", `origin/${beforeBranch}`]);
+    } catch (e) {
+        debug("ignoring error", e);
     }
+    debug(`[after] current branch: ${await currentBranch(afterDir)}`);
 
     debug("folders ready");
 

lib/comparators/git.js

@@ -50,7 +50,7 @@ module.exports = {
     compare: async function(before, after) {
         const beforeSize = await getSize(before.dir);
         const afterSize = await getSize(after.dir);
-        const details = await largestCommits(after.dir, before.branch, after.branch);
+        const details = await largestCommits(after.dir, before.branch, after.sha);
 
         return {
             beforeSize,

test/checkout.test.js

@@ -38,19 +38,28 @@ async function run(dir) {
     assert.equal(await Git(after.dir).revparse(["HEAD"]), commitSha);
 }
 
+function cleanEnvVars() {
+    delete process.env.CI;
+    delete process.env.GITHUB_ACTIONS;
+    delete process.env.GITHUB_BASE_REF;
+    delete process.env.GITHUB_HEAD_REF;
+    delete process.env.TRAVIS;
+    delete process.env.TRAVIS_PULL_REQUEST_BRANCH;
+    delete process.env.TRAVIS_BRANCH;
+    delete process.env.CIRCLECI;
+    delete process.env.CIRCLE_BRANCH;
+}
+
 describe("checkout", function() {
 
     this.captureConsole = true;
 
     beforeEach(function() {
-        delete process.env.CI;
-        delete process.env.GITHUB_ACTIONS;
-        delete process.env.GITHUB_HEAD_REF;
-        delete process.env.TRAVIS;
-        delete process.env.TRAVIS_PULL_REQUEST_BRANCH;
-        delete process.env.TRAVIS_BRANCH;
-        delete process.env.CIRCLECI;
-        delete process.env.CIRCLE_BRANCH;
+        cleanEnvVars();
+    });
+
+    afterEach(function() {
+        cleanEnvVars();
     });
 
     it("handles normal checkouts", async function() {
@@ -74,4 +83,13 @@ describe("checkout", function() {
         process.env.GITHUB_ACTIONS = true;
         await run("test/checkout/githubactions");
     });
+
+    it("handles github action fork PR checkouts", async function() {
+        process.env.CI = "true";
+        process.env.GITHUB_ACTIONS = true;
+        process.env.GITHUB_BASE_REF = "main";
+        // this branch name isn't actually set in test/checkout/githubactions/checkout.sh
+        process.env.GITHUB_HEAD_REF = "some-branch";
+        await run("test/checkout/githubactions");
+    });
 });

test/cli.test.js

@@ -75,7 +75,24 @@ describe("cli e2e", function() {
 
         assert.strictEqual(lastExitCode, undefined);
         assert(this.output.stdout.includes("'main' => 'new'"));
-        assert(this.output.stdout.includes("+ ✅  git: -0.0%"));
+        assert(this.output.stdout.includes("+ ✅  git: -0."));
+    });
+
+    it("fork PR (github actions)", async function() {
+        process.env.CI = "true";
+        process.env.GITHUB_ACTIONS = true;
+        process.env.GITHUB_BASE_REF = "main";
+        // this branch name isn't actually set in the checkout steps in the script
+        process.env.GITHUB_HEAD_REF = "branch";
+
+        await exec(path.join(PROJECT_DIR, "test/scripts/fork.sh"));
+        process.chdir("checkout");
+
+        await sizewatcher();
+
+        assert.strictEqual(lastExitCode, undefined);
+        assert(this.output.stdout.includes("'main' => 'branch'"));
+        assert(this.output.stdout.includes("git:"));
     });
 
 });

test/scripts/fork.sh

@@ -0,0 +1,40 @@
+#!/bin/sh
+
+# simulate a fork PR in github actions
+
+mkdir remote
+cd remote
+REMOTE=$PWD
+
+# setup new git repo
+git init --initial-branch=main
+# needed for git run in CI context where none of this is set
+git config --local user.email "you@example.com"
+git config --local user.name "Your Name"
+
+echo "hello" > file
+git add file
+git commit -a -m "initial commit"
+
+# new local branch
+git checkout -b branch
+echo "hello2" > file
+git commit -a -m "branch commit"
+
+# need the commit hash in the js code, and it's different each run
+git rev-parse HEAD > ../commit.hash
+SHA=$(cat ../commit.hash)
+
+# checkout like github actions
+# actions/checkout@v2 and v3
+
+cd ..
+mkdir checkout
+cd checkout
+
+git init
+git remote add origin $REMOTE
+git config --local gc.auto 0
+git -c protocol.version=2 fetch --no-tags --prune --progress --no-recurse-submodules --depth=1 \
+  origin +$SHA:refs/remotes/pull/1/merge
+git checkout --progress --force refs/remotes/pull/1/merge