add patch header interface

6 files changed, 40 insertions, 3 deletions

diff --git a/patchtree/__init__.py b/patchtree/__init__.py
index e7f3568..f2cc78a 100644
--- a/patchtree/__init__.py
+++ b/patchtree/__init__.py
@@ -1,4 +1,4 @@
-from .config import Config
+from .config import Config, Header
 from .diff import Diff, IgnoreDiff
 from .context import Context
 from .process import ProcessCoccinelle, ProcessJinja2
diff --git a/patchtree/cli.py b/patchtree/cli.py
index f4c0dd1..8f3a48b 100644
--- a/patchtree/cli.py
+++ b/patchtree/cli.py
@@ -51,9 +51,11 @@ def main():
     print("no files to patch!", file=stderr)
     return 0
 
+  config.header(context)
+
   for file in files:
     patch = config.patch(config, file)
-    patch.write_diff(context)
+    patch.write(context)
 
   context.output.flush()
   context.output.close()
diff --git a/patchtree/config.py b/patchtree/config.py
index 11f92f9..23849a9 100644
--- a/patchtree/config.py
+++ b/patchtree/config.py
@@ -1,5 +1,6 @@
 from dataclasses import dataclass, field
 from argparse import ArgumentParser
+from importlib import metadata
 
 from .context import Context
 from .patch import Patch
@@ -16,6 +17,30 @@ DEFAULT_DIFFS: dict[str, type[Diff]] = {
   ".gitignore": IgnoreDiff,
 }
 
+class Header:
+  context: Context
+  name = "patchtree"
+  license = None
+
+  def __init__(self, context: Context):
+    self.context = context
+
+    self.write_version()
+    self.write_version_extra()
+    self.write_license()
+
+  def write_version(self):
+    version = metadata.version("patchtree")
+    self.context.output.write(f"{self.name} output (version {version})\n")
+
+  def write_version_extra(self):
+    pass
+
+  def write_license(self):
+    if self.license is None:
+      return
+    self.context.output.write(f"{self.license}\n")
+
 @dataclass
 class Config:
   context: type[Context] = Context
@@ -24,6 +49,7 @@ class Config:
   process_delimiter: str = "#"
   processors: dict[str, type[Process]] = field(default_factory=lambda: DEFAULT_PROCESSORS)
   diff_strategies: dict[str, type[Diff]] = field(default_factory=lambda: DEFAULT_DIFFS)
+  header: type[Header] = Header
 
   def __post_init__(self):
     self.processors = {**DEFAULT_PROCESSORS, **self.processors}
diff --git a/patchtree/context.py b/patchtree/context.py
index 914b3f1..207b8c2 100644
--- a/patchtree/context.py
+++ b/patchtree/context.py
@@ -22,6 +22,12 @@ class Context:
     if not path.exists(target):
       raise Exception(f"cannot open `{target}'")
 
+    if options.out is not None:
+      if options.out == "-":
+        self.output = stdout
+      else:
+        self.output = open(options.out, "w+")
+
     if path.isdir(target):
       self.fs = DiskPath(target)
     elif is_zipfile(target):
diff --git a/patchtree/patch.py b/patchtree/patch.py
index 86df566..cddf313 100644
--- a/patchtree/patch.py
+++ b/patchtree/patch.py
@@ -54,7 +54,7 @@ class Patch:
       processors.append(self.config.processors[processor])
     return processors
 
-  def write_diff(self, context: Context) -> None:
+  def write(self, context: Context) -> None:
     diff_class = self.get_diff()
     processor_classes = self.get_processors()
 
diff --git a/patchtree/process.py b/patchtree/process.py
index 7170c18..44082cd 100644
--- a/patchtree/process.py
+++ b/patchtree/process.py
@@ -35,6 +35,9 @@ class ProcessCoccinelle(Process):
   def transform(self, content_a, content_b) -> str:
     content_a = content_a or ""
 
+    if len(content_b.strip()) == 0:
+      return content_a
+
     temp_a = Path(mkstemp()[1])
     temp_b = Path(mkstemp()[1])
     temp_sp = Path(mkstemp()[1])