feat: pre-populate commit dialog with heuristic message from git diff

Generate a commit message from modified files (e.g. "Update winter-2026"
or "Update 12 notes") and pre-fill the CommitDialog textarea so users can
commit immediately or edit the suggestion.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/App.tsx

@@ -25,6 +25,7 @@ import { useViewMode } from './hooks/useViewMode'
 import { useEntryActions } from './hooks/useEntryActions'
 import { useAppCommands } from './hooks/useAppCommands'
 import { isEmoji } from './utils/emoji'
+import { generateCommitMessage } from './utils/commitMessage'
 import { useDialogs } from './hooks/useDialogs'
 import { useVaultSwitcher } from './hooks/useVaultSwitcher'
 import { useGitHistory } from './hooks/useGitHistory'
@@ -211,6 +212,7 @@ function App() {
   }, [resolvedPath])
 
   const commitFlow = useCommitFlow({ savePending: appSave.savePending, loadModifiedFiles: vault.loadModifiedFiles, commitAndPush: vault.commitAndPush, setToastMessage, onPushRejected: autoSync.handlePushRejected })
+  const suggestedCommitMessage = useMemo(() => generateCommitMessage(vault.modifiedFiles), [vault.modifiedFiles])
 
   const entryActions = useEntryActions({
     entries: vault.entries, updateEntry: vault.updateEntry,
@@ -468,7 +470,7 @@ function App() {
       <CommandPalette open={dialogs.showCommandPalette} commands={commands} onClose={dialogs.closeCommandPalette} />
       <SearchPanel open={dialogs.showSearch} vaultPath={resolvedPath} entries={vault.entries} onSelectNote={notes.handleSelectNote} onClose={dialogs.closeSearch} />
       <CreateTypeDialog open={dialogs.showCreateTypeDialog} onClose={dialogs.closeCreateType} onCreate={handleCreateType} />
-      <CommitDialog open={commitFlow.showCommitDialog} modifiedCount={vault.modifiedFiles.length} onCommit={commitFlow.handleCommitPush} onClose={commitFlow.closeCommitDialog} />
+      <CommitDialog open={commitFlow.showCommitDialog} modifiedCount={vault.modifiedFiles.length} suggestedMessage={suggestedCommitMessage} onCommit={commitFlow.handleCommitPush} onClose={commitFlow.closeCommitDialog} />
       <ConflictResolverModal
         open={dialogs.showConflictResolver}
         fileStates={conflictResolver.fileStates}

src/components/CommitDialog.test.tsx

@@ -78,4 +78,30 @@ describe('CommitDialog', () => {
     const { container } = render(<CommitDialog open={false} modifiedCount={3} onCommit={onCommit} onClose={onClose} />)
     expect(container.querySelector('textarea')).toBeNull()
   })
+
+  it('pre-populates message with suggestedMessage', () => {
+    render(<CommitDialog open={true} modifiedCount={3} suggestedMessage="Update alpha, beta" onCommit={onCommit} onClose={onClose} />)
+    const textarea = screen.getByPlaceholderText('Commit message...')
+    expect(textarea).toHaveValue('Update alpha, beta')
+  })
+
+  it('enables Commit button when suggestedMessage is provided', () => {
+    render(<CommitDialog open={true} modifiedCount={3} suggestedMessage="Update alpha" onCommit={onCommit} onClose={onClose} />)
+    expect(getCommitButton()).not.toBeDisabled()
+  })
+
+  it('submits suggestedMessage on Cmd+Enter without user edits', () => {
+    render(<CommitDialog open={true} modifiedCount={3} suggestedMessage="Update alpha" onCommit={onCommit} onClose={onClose} />)
+    const textarea = screen.getByPlaceholderText('Commit message...')
+    fireEvent.keyDown(textarea, { key: 'Enter', metaKey: true })
+    expect(onCommit).toHaveBeenCalledWith('Update alpha')
+  })
+
+  it('allows user to edit the suggested message', () => {
+    render(<CommitDialog open={true} modifiedCount={3} suggestedMessage="Update alpha" onCommit={onCommit} onClose={onClose} />)
+    const textarea = screen.getByPlaceholderText('Commit message...')
+    fireEvent.change(textarea, { target: { value: 'fix: corrected typo in alpha' } })
+    fireEvent.click(getCommitButton())
+    expect(onCommit).toHaveBeenCalledWith('fix: corrected typo in alpha')
+  })
 })

src/components/CommitDialog.tsx

@@ -6,20 +6,21 @@ import { Badge } from '@/components/ui/badge'
 interface CommitDialogProps {
   open: boolean
   modifiedCount: number
+  suggestedMessage?: string
   onCommit: (message: string) => void
   onClose: () => void
 }
 
-export function CommitDialog({ open, modifiedCount, onCommit, onClose }: CommitDialogProps) {
+export function CommitDialog({ open, modifiedCount, suggestedMessage, onCommit, onClose }: CommitDialogProps) {
   const [message, setMessage] = useState('')
   const inputRef = useRef<HTMLTextAreaElement>(null)
 
   useEffect(() => {
     if (open) {
-      setMessage('') // eslint-disable-line react-hooks/set-state-in-effect -- reset on dialog open
+      setMessage(suggestedMessage ?? '') // eslint-disable-line react-hooks/set-state-in-effect -- reset on dialog open
       setTimeout(() => inputRef.current?.focus(), 50)
     }
-  }, [open])
+  }, [open]) // eslint-disable-line react-hooks/exhaustive-deps -- only reset when dialog opens
 
   const handleSubmit = () => {
     const trimmed = message.trim()

src/utils/commitMessage.test.ts

@@ -0,0 +1,73 @@
+import { describe, it, expect } from 'vitest'
+import { generateCommitMessage } from './commitMessage'
+import type { ModifiedFile } from '../types'
+
+function file(relativePath: string, status: ModifiedFile['status'] = 'modified'): ModifiedFile {
+  return { path: `/vault/${relativePath}`, relativePath, status }
+}
+
+describe('generateCommitMessage', () => {
+  it('returns empty string for no files', () => {
+    expect(generateCommitMessage([])).toBe('')
+  })
+
+  it('uses note title for a single modified file', () => {
+    expect(generateCommitMessage([file('winter-2026.md')])).toBe('Update winter-2026')
+  })
+
+  it('strips .md extension from the name', () => {
+    expect(generateCommitMessage([file('thoughts-on-testing.md')])).toBe('Update thoughts-on-testing')
+  })
+
+  it('uses basename for files in subdirectories', () => {
+    expect(generateCommitMessage([file('notes/deep/idea.md')])).toBe('Update idea')
+  })
+
+  it('lists 2 files comma-separated', () => {
+    const msg = generateCommitMessage([file('alpha.md'), file('beta.md')])
+    expect(msg).toBe('Update alpha, beta')
+  })
+
+  it('lists 3 files comma-separated', () => {
+    const msg = generateCommitMessage([
+      file('alpha.md'),
+      file('beta.md'),
+      file('gamma.md'),
+    ])
+    expect(msg).toBe('Update alpha, beta, gamma')
+  })
+
+  it('uses count for 4+ files', () => {
+    const msg = generateCommitMessage([
+      file('a.md'),
+      file('b.md'),
+      file('c.md'),
+      file('d.md'),
+    ])
+    expect(msg).toBe('Update 4 notes')
+  })
+
+  it('says "Add" for a single new/untracked file', () => {
+    expect(generateCommitMessage([file('new-idea.md', 'untracked')])).toBe('Add new-idea')
+  })
+
+  it('says "Add" for a single added file', () => {
+    expect(generateCommitMessage([file('new-idea.md', 'added')])).toBe('Add new-idea')
+  })
+
+  it('says "Delete" for a single deleted file', () => {
+    expect(generateCommitMessage([file('old-note.md', 'deleted')])).toBe('Delete old-note')
+  })
+
+  it('says "Rename" for a single renamed file', () => {
+    expect(generateCommitMessage([file('renamed.md', 'renamed')])).toBe('Rename renamed')
+  })
+
+  it('uses "Update" when statuses are mixed', () => {
+    const msg = generateCommitMessage([
+      file('alpha.md', 'modified'),
+      file('beta.md', 'untracked'),
+    ])
+    expect(msg).toBe('Update alpha, beta')
+  })
+})

src/utils/commitMessage.ts

@@ -0,0 +1,33 @@
+import type { ModifiedFile } from '../types'
+
+const VERB_MAP: Record<string, string> = {
+  modified: 'Update',
+  added: 'Add',
+  untracked: 'Add',
+  deleted: 'Delete',
+  renamed: 'Rename',
+}
+
+const MAX_LISTED_FILES = 3
+
+function noteName(relativePath: string): string {
+  const basename = relativePath.split('/').pop() ?? relativePath
+  return basename.replace(/\.md$/, '')
+}
+
+function verb(files: ModifiedFile[]): string {
+  const statuses = new Set(files.map((f) => f.status))
+  if (statuses.size === 1) return VERB_MAP[files[0].status] ?? 'Update'
+  return 'Update'
+}
+
+/** Generate a heuristic commit message from modified files. */
+export function generateCommitMessage(files: ModifiedFile[]): string {
+  if (files.length === 0) return ''
+  const action = verb(files)
+  if (files.length <= MAX_LISTED_FILES) {
+    const names = files.map((f) => noteName(f.relativePath)).join(', ')
+    return `${action} ${names}`
+  }
+  return `${action} ${files.length} notes`
+}