From 0867121734b9075be8f09f91889deb7291d61e75 Mon Sep 17 00:00:00 2001
From: YongxinFu <190456533+YongxinFu@users.noreply.github.com>
Date: Sat, 17 Oct 2026 09:52:20 +0800
Subject: [PATCH] feat: save markdown output to a file

Assisted-by: Codex (OpenAI)
---
 README.md           |  2 +-
 src/diffnote/cli.py | 18 ++++++++++++++++--
 tests/test_cli.py   | 19 +++++++++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 2b6200b..120efd7 100644
--- a/README.md
+++ b/README.md
@@ -87,6 +87,7 @@ In any git repository with changes:
 diffnote                 # pretty terminal summary of your working tree
 diffnote --staged        # only staged changes
 diffnote --markdown      # GitHub PR-body markdown (paste-ready)
+diffnote --markdown --save out.md # write the PR body to a file, without stdout output
 diffnote --commits 5     # summarize the last 5 commits
 diffnote --base main     # changes vs main (great for PR prep)
 diffnote --json          # machine-readable, for CI
@@ -134,7 +135,6 @@ and then only to `localhost` (your Ollama).
 
 ## Roadmap
 
-- [ ] `--save` to write markdown straight into a PR template
 - [ ] Breaking-change detection (`feat!:` / public API paths)
 - [ ] `--stats` per-area totals
 - [ ] Plugin hooks for custom risk rules
diff --git a/src/diffnote/cli.py b/src/diffnote/cli.py
index 20961be..b4f1171 100644
--- a/src/diffnote/cli.py
+++ b/src/diffnote/cli.py
@@ -28,6 +28,8 @@ def build_parser():
     fmt = p.add_argument_group("output")
     fmt.add_argument("--markdown", action="store_true",
                      help="Print a GitHub PR-body markdown.")
+    fmt.add_argument("--save", metavar="PATH",
+                     help="Write markdown output to PATH instead of stdout (requires --markdown).")
     fmt.add_argument("--json", action="store_true",
                      help="Print machine-readable JSON.")
     fmt.add_argument("--no-color", action="store_true",
@@ -51,7 +53,10 @@ def get_diff(args, cwd):
 
 
 def main(argv=None):
-    args = build_parser().parse_args(argv)
+    parser = build_parser()
+    args = parser.parse_args(argv)
+    if args.save and (not args.markdown or args.json):
+        parser.error("--save requires --markdown and cannot be used with --json")
     try:
         cwd = gitutil.repo_root()
     except gitutil.GitError as exc:
@@ -85,7 +90,16 @@ def main(argv=None):
     if args.json:
         print(render.render_json(summary, llm_prose))
     elif args.markdown:
-        print(render.render_markdown(summary, llm_prose))
+        markdown = render.render_markdown(summary, llm_prose)
+        if args.save:
+            try:
+                with open(args.save, "w", encoding="utf-8", newline="\n") as output_file:
+                    output_file.write(markdown + "\n")
+            except OSError as exc:
+                print(f"diffnote: could not write {args.save}: {exc}", file=sys.stderr)
+                return 1
+        else:
+            print(markdown)
     else:
         print(render.render_terminal(summary, use_color=not args.no_color, llm_prose=llm_prose))
     return 0
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 1cc13d6..652ec8a 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -72,6 +72,25 @@ def test_markdown_output(capsys):
     assert "## Changes" in out
 
 
+def test_save_markdown_writes_file_without_stdout(capsys):
+    d = _make_dirty_repo()
+    output_path = os.path.join(d, "pr-body.md")
+    old = os.getcwd()
+    os.chdir(d)
+    try:
+        rc = cli.main(["--save", output_path, "--markdown"])
+    finally:
+        os.chdir(old)
+    captured = capsys.readouterr()
+    with open(output_path, encoding="utf-8") as output_file:
+        saved = output_file.read()
+    assert rc == 0
+    assert captured.out == ""
+    assert "## Summary" in saved
+    assert "## Changes" in saved
+    assert saved.endswith("\n")
+
+
 def test_no_changes(capsys):
     import os
     d = tempfile.mkdtemp()