fix failure on fork PRs

For after checkout, always use local cloning and do not checkout
afterBranch as it will be automatically present in the local clone.

The git comparator also had to be adopted to always use the sha
instead of the git branch for after.

Add unit test fork.sh.

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