packet line writer deals with long lines and definitely isn't smart

…so it doesn't do anything on drop.

README.md

@@ -123,7 +123,7 @@ Please see _'Development Status'_ for a listing of all crates and their capabili
   * [x] [V2 additions](https://github.com/git/git/blob/master/Documentation/technical/protocol-v2.txt#L35:L36)
   * [x] [side-band mode](https://github.com/git/git/blob/master/Documentation/technical/pack-protocol.txt#L467:L467)
   * [x] `Read` from packet line with (optional) progress support via sidebands
-  * [ ] `Write` with built-in packet line encoding
+  * [x] `Write` with built-in packet line encoding
 
 ### git-transport
   * [ ] general purpose `connect(…)` for clients

git-packetline/src/write.rs

@@ -1,3 +1,4 @@
+use crate::MAX_DATA_LEN;
 use std::io;
 
 /// An implementor of `Write` which passes all input to an inner `Write` in packet line data encoding, one line per `write(…)`
@@ -22,28 +23,34 @@ impl<T: io::Write> Writer<T> {
 }
 
 impl<T: io::Write> io::Write for Writer<T> {
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+    fn write(&mut self, mut buf: &[u8]) -> io::Result<usize> {
         if buf.is_empty() {
             return Err(io::Error::new(
                 io::ErrorKind::Other,
                 "empty packet lines are not permitted as '0004' is invalid",
             ));
         }
 
-        if self.binary {
-            crate::encode::data_to_write(buf, &mut self.inner)
-        } else {
-            crate::encode::text_to_write(buf, &mut self.inner)
-        }
-        .map_err(|err| {
-            use crate::encode::Error::*;
-            match err {
-                Io(err) => err,
-                DataIsEmpty | DataLengthLimitExceeded(_) => {
-                    unreachable!("We are handling empty and large data here, so this can't ever happen")
-                }
+        let mut written = 0;
+        while !buf.is_empty() {
+            let (data, rest) = buf.split_at(buf.len().min(MAX_DATA_LEN));
+            written += if self.binary {
+                crate::encode::data_to_write(data, &mut self.inner)
+            } else {
+                crate::encode::text_to_write(data, &mut self.inner)
             }
-        })
+            .map_err(|err| {
+                use crate::encode::Error::*;
+                match err {
+                    Io(err) => err,
+                    DataIsEmpty | DataLengthLimitExceeded(_) => {
+                        unreachable!("We are handling empty and large data here, so this can't ever happen")
+                    }
+                }
+            })?;
+            buf = rest;
+        }
+        Ok(written)
     }
 
     fn flush(&mut self) -> io::Result<()> {

git-packetline/tests/packet_line/write.rs

@@ -44,3 +44,11 @@ fn empty_writes_fail_with_error() {
         "empty packet lines are not permitted as '0004' is invalid"
     )
 }
+
+#[test]
+fn nothing_happens_on_drop() {
+    let mut out = Vec::new();
+    let w = Writer::new(&mut out);
+    drop(w);
+    assert!(out.is_empty());
+}

tasks.md

@@ -12,7 +12,7 @@
       * [x] Disable sideband support (e.g. github http V2 doesn't have it)
     * [x] don't coerce line delimiters into empty slices.
     * [x] Make 'ERR <error>' handling as error optional, as it may occur only in certain contexts.
-    * [ ] `Write` with packet line encoding
+    * [x] `Write` with packet line encoding
   * **git-url**
     * [ ] parse into components to make them easy to understand
   * **connect**