add options to keep metadata from either old or new file or none of them

.gitignore

@@ -3,3 +3,4 @@ node_modules/
 lib/
 .mocharc.yml
 *.pdf
+test/*.actual

README.md

@@ -85,6 +85,7 @@ Usage: pandiff [OPTIONS] FILE1 FILE2
   -t, --to=FORMAT
   -v, --version
       --wrap=STRING
+      --metadata
 ```
 
 ### Git integration

src/cli.ts

@@ -54,6 +54,7 @@ const optionDefinitions: commandLineArgs.OptionDefinition[] = [
   {name: 'version', alias: 'v', type: Boolean},
   {name: 'wrap', type: String},
   {name: 'files', multiple: true, defaultOption: true},
+  {name: 'metadata', type: String},
 ];
 
 function help() {

src/index.spec.ts

@@ -159,3 +159,84 @@ describe('Misc', () => {
     expectWithFallback(output, expected, 'test/diff-table.html');
   });
 });
+
+describe('Metadata', () => {
+  it('keep metadata from old document', async () => {
+    const output = await pandiff(
+      'test/old-metadata.md',
+      'test/new-metadata.md',
+      {
+        files: true,
+        metadata: 'old',
+        to: 'markdown',
+      }
+    );
+    const expected = fs.readFileSync('test/keep-old-metadata-diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep metadata from new document', async () => {
+    const output = await pandiff(
+      'test/old-metadata.md',
+      'test/new-metadata.md',
+      {
+        files: true,
+        metadata: 'new',
+        to: 'markdown',
+      }
+    );
+    const expected = fs.readFileSync('test/keep-new-metadata-diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep metadata from no document', async () => {
+    const output = await pandiff(
+      'test/old-metadata.md',
+      'test/new-metadata.md',
+      {
+        files: true,
+        metadata: 'none',
+        to: 'markdown',
+      }
+    );
+    const expected = fs.readFileSync('test/keep-no-metadata-diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep metadata from old document without metadata', async () => {
+    const output = await pandiff('test/old.md', 'test/new.md', {
+      files: true,
+      metadata: 'old',
+      to: 'markdown',
+    });
+    const expected = fs.readFileSync('test/diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep metadata from new document without metadata', async () => {
+    const output = await pandiff('test/old.md', 'test/new.md', {
+      files: true,
+      metadata: 'new',
+      to: 'markdown',
+    });
+    const expected = fs.readFileSync('test/diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep metadata none document without metadata', async () => {
+    const output = await pandiff('test/old.md', 'test/new.md', {
+      files: true,
+      metadata: 'none',
+      to: 'markdown',
+    });
+    const expected = fs.readFileSync('test/diff.md', 'utf8');
+    expect(output, expected);
+  });
+  it('keep no metadata if metadata is not specified', async () => {
+    const output = await pandiff(
+      'test/old-metadata.md',
+      'test/new-metadata.md',
+      {
+        files: true,
+        to: 'markdown',
+      }
+    );
+    const expected = fs.readFileSync('test/keep-no-metadata-diff.md', 'utf8');
+    expect(output, expected);
+  });
+});

src/index.ts

@@ -263,11 +263,38 @@ async function convert(source: string, opts: pandiff.Options = {}) {
   return html;
 }
 
+async function extractMetadata(source: string) {
+  const file = fs.readFileSync(source, 'utf8');
+  const lines = file.split('\n');
+  if (lines[0].trim() !== '---') return '';
+
+  const metadata = [lines[0]];
+  for (let i = 1; i < lines.length; i++) {
+    metadata.push(lines[i]);
+    if (lines[i].trim() === '---') break;
+  }
+
+  return metadata.join('\n') + '\n';
+}
+
 async function pandiff(
   source1: string,
   source2: string,
   opts: pandiff.Options = {}
 ): Promise<string | null> {
+  let metadata = '';
+  switch (opts.metadata) {
+    case 'old':
+      opts.standalone = true;
+      metadata = await extractMetadata(source1);
+      break;
+    case 'new':
+      opts.standalone = true;
+      metadata = await extractMetadata(source2);
+      break;
+    default:
+      break;
+  }
   const html1 = await convert(source1, opts);
   const html2 = await convert(source2, opts);
   const html = htmldiff(html1, html2);
@@ -282,7 +309,7 @@ async function pandiff(
     );
     return null;
   } else {
-    return render(html, opts);
+    return render(html, opts, metadata);
   }
 }
 
@@ -319,7 +346,7 @@ const regex = {
   },
 };
 
-async function render(html: string, opts: pandiff.Options = {}) {
+async function render(html: string, opts: pandiff.Options = {}, metadata = '') {
   html = postprocess(html);
   const args = buildArgs(opts, 'reference-links');
   args.push('--wrap=none');
@@ -357,7 +384,7 @@ async function render(html: string, opts: pandiff.Options = {}) {
     }
   }
   const text = lines.join('\n');
-  return postrender(text, opts);
+  return postrender(text, opts, metadata);
 }
 
 const criticHTML = (text: string) =>
@@ -411,8 +438,12 @@ const pandocOptionsHTML = [
   '--standalone',
 ];
 
-async function postrender(text: string, opts: pandiff.Options = {}) {
-  if (!opts.output && !opts.to) return text;
+async function postrender(
+  text: string,
+  opts: pandiff.Options = {},
+  metadata = ''
+) {
+  if (!opts.output && !opts.to) return `${metadata}${text}`;
 
   if (!('highlight-style' in opts)) opts['highlight-style'] = 'kate';
   let args = buildArgs(
@@ -446,19 +477,21 @@ async function postrender(text: string, opts: pandiff.Options = {}) {
     if (opts.standalone) args = args.concat(pandocOptionsHTML);
   }
 
+  if (opts.standalone) args = args.concat('-s');
+
   if (opts.output) {
-    await sh.pandoc(...args).end(text);
+    await sh.pandoc(...args).end(`${metadata}${text}`);
     return null;
   } else {
     return sh
       .pandoc(...args)
-      .end(text)
+      .end(`${metadata}${text}`)
       .toString();
   }
 }
 
 export = pandiff;
-namespace pandiff { // eslint-disable-line
+  namespace pandiff { // eslint-disable-line
   export type File = string;
   export type Format = string;
   export type Path = string;
@@ -484,6 +517,7 @@ namespace pandiff { // eslint-disable-line
     version?: boolean;
     wrap?: 'auto' | 'none' | 'preserve';
     files?: boolean;
+    metadata?: 'new' | 'old' | 'none';
   }
   /* eslint-disable no-inner-declarations */
   export async function trackChanges(

test/keep-new-metadata-diff.md

@@ -0,0 +1,15 @@
+---
+title: New Title
+---
+
+# {\~~Some~\>Differnt\~\~} Text
+
+Lorem {--ipsum --}dolor sit {~~amet,\~\>amet test,~~} consetetur
+sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et
+dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et
+justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea
+takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit
+amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
+invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.

test/keep-no-metadata-diff.md

@@ -0,0 +1,11 @@
+# {\~~Some~\>Differnt\~\~} Text
+
+Lorem {--ipsum --}dolor sit {~~amet,\~\>amet test,~~} consetetur
+sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et
+dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et
+justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea
+takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit
+amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
+invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.

test/keep-old-metadata-diff.md

@@ -0,0 +1,15 @@
+---
+title: Old Title
+---
+
+# {\~~Some~\>Differnt\~\~} Text
+
+Lorem {--ipsum --}dolor sit {~~amet,\~\>amet test,~~} consetetur
+sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et
+dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et
+justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea
+takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit
+amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
+invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
+vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd
+gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.

test/new-metadata.md

@@ -0,0 +1,6 @@
+---
+title: New Title
+---
+
+# Differnt Text
+Lorem dolor sit amet test, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.

test/old-metadata.md

@@ -0,0 +1,6 @@
+---
+title: Old Title
+---
+
+# Some Text
+Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.