feat: support checkout on a commit in addition to a ref

__test__/create-or-update-branch.int.test.ts

@@ -1,4 +1,8 @@
-import {createOrUpdateBranch, tryFetch} from '../lib/create-or-update-branch'
+import {
+  createOrUpdateBranch,
+  tryFetch,
+  getWorkingBaseAndType
+} from '../lib/create-or-update-branch'
 import * as fs from 'fs'
 import {GitCommandManager} from '../lib/git-command-manager'
 import * as path from 'path'
@@ -193,6 +197,21 @@ describe('create-or-update-branch tests', () => {
     expect(await tryFetch(git, REMOTE_NAME, NOT_EXIST_BRANCH)).toBeFalsy()
   })
 
+  it('tests getWorkingBaseAndType on a checked out ref', async () => {
+    const [workingBase, workingBaseType] = await getWorkingBaseAndType(git)
+    expect(workingBase).toEqual(BASE)
+    expect(workingBaseType).toEqual('branch')
+  })
+
+  it('tests getWorkingBaseAndType on a checked out commit', async () => {
+    // Checkout the HEAD commit SHA
+    const headSha = await git.revParse('HEAD')
+    await git.exec(['checkout', headSha])
+    const [workingBase, workingBaseType] = await getWorkingBaseAndType(git)
+    expect(workingBase).toEqual(headSha)
+    expect(workingBaseType).toEqual('commit')
+  })
+
   it('tests no changes resulting in no new branch being created', async () => {
     const commitMessage = uuidv4()
     const result = await createOrUpdateBranch(
@@ -1450,4 +1469,133 @@ describe('create-or-update-branch tests', () => {
       await gitLogMatches([_commitMessage, INIT_COMMIT_MESSAGE])
     ).toBeTruthy()
   })
+
+  // Working Base is Not a Ref (WBNR)
+  // A commit is checked out leaving the repository in a "detached HEAD" state
+
+  it('tests create and update in detached HEAD state (WBNR)', async () => {
+    // Checkout the HEAD commit SHA
+    const headSha = await git.revParse('HEAD')
+    await git.checkout(headSha)
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false
+    )
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Checkout the HEAD commit SHA
+    const _headSha = await git.revParse('HEAD')
+    await git.checkout(_headSha)
+
+    // Create tracked and untracked file changes
+    const _changes = await createChanges()
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false
+    )
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([_commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+  })
+
+  it('tests create and update with commits on the base inbetween, in detached HEAD state (WBNR)', async () => {
+    // Checkout the HEAD commit SHA
+    const headSha = await git.revParse('HEAD')
+    await git.checkout(headSha)
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false
+    )
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Create commits on the base
+    const commitsOnBase = await createCommits(git)
+    await git.push([
+      '--force',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${DEFAULT_BRANCH}`
+    ])
+
+    // Checkout the HEAD commit SHA
+    const _headSha = await git.revParse('HEAD')
+    await git.checkout(_headSha)
+
+    // Create tracked and untracked file changes
+    const _changes = await createChanges()
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false
+    )
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([
+        _commitMessage,
+        ...commitsOnBase.commitMsgs,
+        INIT_COMMIT_MESSAGE
+      ])
+    ).toBeTruthy()
+  })
 })