fix: skip backup stash when using the --diff option

README.md

@@ -92,7 +92,8 @@ Options:
   -c, --config [path]                path to configuration file, or - to read from stdin
   --cwd [path]                       run all tasks in specific directory, instead of the current
   -d, --debug                        print additional debug information (default: false)
-  --diff [string]                    override the default "--staged" flag of "git diff" to get list of files
+  --diff [string]                    override the default "--staged" flag of "git diff" to get list of files. Implies
+                                     "--no-stash".
   --diff-filter [string]             override the default "--diff-filter=ACMR" flag of "git diff" to get list of files
   --max-arg-length [number]          maximum length of the command-line argument string (default: 0)
   --no-stash                         disable the backup stash, and do not revert in case of errors

bin/lint-staged.js

@@ -44,7 +44,7 @@ cli.option('-d, --debug', 'print additional debug information', false)
 
 cli.option(
   '--diff [string]',
-  'override the default "--staged" flag of "git diff" to get list of files'
+  'override the default "--staged" flag of "git diff" to get list of files. Implies "--no-stash".'
 )
 
 cli.option(

lib/index.js

@@ -86,26 +86,25 @@ const lintStaged = async (
   debugLog('Unset GIT_LITERAL_PATHSPECS (was `%s`)', process.env.GIT_LITERAL_PATHSPECS)
   delete process.env.GIT_LITERAL_PATHSPECS
 
+  const options = {
+    allowEmpty,
+    concurrent,
+    configObject,
+    configPath,
+    cwd,
+    debug,
+    diff,
+    diffFilter,
+    maxArgLength,
+    quiet,
+    relative,
+    shell,
+    stash,
+    verbose,
+  }
+
   try {
-    const ctx = await runAll(
-      {
-        allowEmpty,
-        concurrent,
-        configObject,
-        configPath,
-        cwd,
-        debug,
-        diff,
-        diffFilter,
-        maxArgLength,
-        quiet,
-        relative,
-        shell,
-        stash,
-        verbose,
-      },
-      logger
-    )
+    const ctx = await runAll(options, logger)
     debugLog('Tasks were executed successfully!')
     printTaskOutput(ctx, logger)
     return true

lib/messages.js

@@ -28,8 +28,14 @@ export const NO_STAGED_FILES = `${info} No staged files found.`
 
 export const NO_TASKS = `${info} No staged files match any configured task.`
 
-export const skippingBackup = (hasInitialCommit) => {
-  const reason = hasInitialCommit ? '`--no-stash` was used' : 'there’s no initial commit yet'
+export const skippingBackup = (hasInitialCommit, diff) => {
+  const reason =
+    diff !== undefined
+      ? '`--diff` was used'
+      : hasInitialCommit
+      ? '`--no-stash` was used'
+      : 'there’s no initial commit yet'
+
   return yellow(`${warning} Skipping backup because ${reason}.\n`)
 }
 

lib/runAll.js

@@ -104,10 +104,11 @@ export const runAll = async (
     .then(() => true)
     .catch(() => false)
 
-  // Lint-staged should create a backup stash only when there's an initial commit
-  ctx.shouldBackup = hasInitialCommit && stash
+  // Lint-staged should create a backup stash only when there's an initial commit,
+  // and when using the default list of staged files
+  ctx.shouldBackup = hasInitialCommit && stash && diff === undefined
   if (!ctx.shouldBackup) {
-    logger.warn(skippingBackup(hasInitialCommit))
+    logger.warn(skippingBackup(hasInitialCommit, diff))
   }
 
   const files = await getStagedFiles({ cwd: gitDir, diff, diffFilter })

test/runAll.spec.js

@@ -45,6 +45,7 @@ describe('runAll', () => {
 
   beforeAll(() => {
     console = makeConsoleMock()
+    jest.clearAllMocks()
   })
 
   afterEach(() => {
@@ -372,4 +373,14 @@ describe('runAll', () => {
       expect(ctx.errors.has(ConfigNotFoundError)).toBe(true)
     }
   })
+
+  it('should warn when --no-stash was used', async () => {
+    await runAll({ configObject: { '*.js': ['echo "sample"'] }, stash: false })
+    expect(console.printHistory()).toMatch('Skipping backup because `--no-stash` was used')
+  })
+
+  it('should warn when --diff was used', async () => {
+    await runAll({ configObject: { '*.js': ['echo "sample"'] }, diff: 'branch1...branch2' })
+    expect(console.printHistory()).toMatch('Skipping backup because `--diff` was used')
+  })
 })