From e936da2ec5a175f18f1f32b22946cdf3d777840e Mon Sep 17 00:00:00 2001
From: Seraphina Orsini <orsini.seraphina@gmail.com>
Date: Fri, 3 Jul 2020 05:41:00 -0400
Subject: [PATCH] Use `git diff` instead of `git log` for --changedSince
 (#10155)

---
 CHANGELOG.md                                  |  1 +
 .../jestChangedFiles.test.ts.snap             |  2 +-
 e2e/__tests__/jestChangedFiles.test.ts        | 45 ++++++++++++++++++-
 packages/jest-changed-files/src/git.ts        | 10 ++---
 4 files changed, 49 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73616e2902d9..ba03e914b1be 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Fixes
 
 - `[expect]` Match symbols and bigints in `any()` ([#10223](https://github.com/facebook/jest/pull/10223))
+- `[jest-changed-files]` Use `git diff` instead of `git log` for `--changedSince` ([#10155](https://github.com/facebook/jest/pull/10155))
 - `[jest-console]` Add missing console.timeLog for compatability with Node ([#10209](https://github.com/facebook/jest/pull/10209))
 - `[jest-snapshot]` Strip added indentation for inline error snapshots ([#10217](https://github.com/facebook/jest/pull/10217))
 
diff --git a/e2e/__tests__/__snapshots__/jestChangedFiles.test.ts.snap b/e2e/__tests__/__snapshots__/jestChangedFiles.test.ts.snap
index cbbd571d60a3..3091b28da28d 100644
--- a/e2e/__tests__/__snapshots__/jestChangedFiles.test.ts.snap
+++ b/e2e/__tests__/__snapshots__/jestChangedFiles.test.ts.snap
@@ -5,7 +5,7 @@ exports[`handles a bad revision for "changedSince", for git 1`] = `
 
   ● Test suite failed to run
 
-    fatal: bad revision '^blablabla'
+    fatal: bad revision '^blablabla...HEAD'
 
 `;
 
diff --git a/e2e/__tests__/jestChangedFiles.test.ts b/e2e/__tests__/jestChangedFiles.test.ts
index 480e1d966187..45e04eeda08d 100644
--- a/e2e/__tests__/jestChangedFiles.test.ts
+++ b/e2e/__tests__/jestChangedFiles.test.ts
@@ -254,6 +254,49 @@ test('monitors only root paths for git', async () => {
   ).toEqual(['file2.txt', 'file3.txt']);
 });
 
+it('does not find changes in files with no diff, for git', async () => {
+  const roots = [path.resolve(DIR)];
+
+  // create an empty file, commit it to "master"
+  writeFiles(DIR, {
+    'file1.txt': '',
+  });
+  run(`${GIT} init`, DIR);
+  run(`${GIT} add file1.txt`, DIR);
+  run(`${GIT} commit --no-gpg-sign -m "initial"`, DIR);
+
+  // check out a new branch, jestChangedFilesSpecBase, to use later in diff
+  run(`${GIT} checkout -b jestChangedFilesSpecBase`, DIR);
+
+  // check out second branch, jestChangedFilesSpecMod, modify file & commit
+  run(`${GIT} checkout -b jestChangedFilesSpecMod`, DIR);
+  writeFiles(DIR, {
+    'file1.txt': 'modified file1',
+  });
+  run(`${GIT} add file1.txt`, DIR);
+  run(`${GIT} commit --no-gpg-sign -m "modified"`, DIR);
+
+  // still on jestChangedFilesSpecMod branch, "revert" back to empty file and commit
+  writeFiles(DIR, {
+    'file1.txt': '',
+  });
+  run(`${GIT} add file1.txt`, DIR);
+  run(`${GIT} commit --no-gpg-sign -m "removemod"`, DIR);
+
+  // check that passing in no changedSince arg doesn't return any unstaged / other changes
+  const {changedFiles: files} = await getChangedFilesForRoots(roots, {});
+  expect(Array.from(files)).toEqual([]);
+
+  // check that in diff from `jestChangedFilesSpecBase` branch, no changed files are reported
+  const {changedFiles: filesExplicitBaseBranch} = await getChangedFilesForRoots(
+    roots,
+    {
+      changedSince: 'jestChangedFilesSpecBase',
+    },
+  );
+  expect(Array.from(filesExplicitBaseBranch)).toEqual([]);
+});
+
 test('handles a bad revision for "changedSince", for git', async () => {
   writeFiles(DIR, {
     '.watchmanconfig': '',
@@ -266,7 +309,7 @@ test('handles a bad revision for "changedSince", for git', async () => {
   run(`${GIT} add .`, DIR);
   run(`${GIT} commit --no-gpg-sign -m "first"`, DIR);
 
-  const {exitCode, stderr} = runJest(DIR, ['--changedSince=blablabla']);
+  const {exitCode, stderr} = runJest(DIR, ['--changedSince=^blablabla']);
 
   expect(exitCode).toBe(1);
   expect(wrap(stderr)).toMatchSnapshot();
diff --git a/packages/jest-changed-files/src/git.ts b/packages/jest-changed-files/src/git.ts
index 919eb19be98d..da1329a77bbb 100644
--- a/packages/jest-changed-files/src/git.ts
+++ b/packages/jest-changed-files/src/git.ts
@@ -54,13 +54,9 @@ const adapter: SCMAdapter = {
     if (changedSince) {
       const [committed, staged, unstaged] = await Promise.all([
         findChangedFilesUsingCommand(
-          [
-            'log',
-            '--name-only',
-            '--pretty=format:',
-            'HEAD',
-            `^${changedSince}`,
-          ].concat(includePaths),
+          ['diff', '--name-only', `${changedSince}...HEAD`].concat(
+            includePaths,
+          ),
           cwd,
         ),
         findChangedFilesUsingCommand(