Fix PatchUtil for parsing special patch format

`diff` generate incomplete header for adding or removing one line file.
Eg.
"""
--- foo
+++ bar
@@ -1 +0,0 @@  # Should be @@ -1,1 +0,0 @@
-hello, world
"""

We set the default value to 1 when the size info is missing.
Similar logic in `git apply` implementation:
https://github.com/git/git/blob/5fa0f5238b0cd46cfe7f6fa76c3f526ea98148d9/apply.c#L1400

Fixes #9222

RELNOTES: None
PiperOrigin-RevId: 264799477

src/main/java/com/google/devtools/build/lib/bazel/repository/PatchUtil.java

@@ -64,8 +64,11 @@ public Result check(int oldLineCnt, int newLineCnt) {
     ChunkHeader(String header) throws PatchFailedException {
       Matcher m = CHUNK_HEADER_RE.matcher(header);
       if (m.find()) {
-        oldSize = Integer.parseInt(m.group(2));
-        newSize = Integer.parseInt(m.group(4));
+        String size;
+        size = m.group(2);
+        oldSize = (size == null) ? 1 : Integer.parseInt(size);
+        size = m.group(4);
+        newSize = (size == null) ? 1 : Integer.parseInt(size);
       } else {
         throw new PatchFailedException("Wrong chunk header: " + header);
       }

src/test/java/com/google/devtools/build/lib/bazel/repository/PatchUtilTest.java

@@ -65,6 +65,24 @@ public void testAddFile() throws IOException, PatchFailedException {
     assertThat(PatchUtil.readFile(newFile)).containsExactlyElementsIn(newFileContent);
   }
 
+  @Test
+  public void testAddOneLineFile() throws IOException, PatchFailedException {
+    Path patchFile =
+        scratch.file(
+            "/root/patchfile",
+            "diff --git a/newfile b/newfile",
+            "new file mode 100644",
+            "index 0000000..f742c88",
+            "--- /dev/null",
+            "+++ b/newfile",
+            "@@ -0,0 +1 @@", // diff will produce such chunk header for one line file.
+            "+hello, world");
+    PatchUtil.apply(patchFile, 1, root);
+    Path newFile = root.getRelative("newfile");
+    ImmutableList<String> newFileContent = ImmutableList.of("hello, world");
+    assertThat(PatchUtil.readFile(newFile)).containsExactlyElementsIn(newFileContent);
+  }
+
   @Test
   public void testDeleteFile() throws IOException, PatchFailedException {
     Path oldFile = scratch.file("/root/oldfile", "I'm an old file", "bye, world");
@@ -80,6 +98,20 @@ public void testDeleteFile() throws IOException, PatchFailedException {
     assertThat(oldFile.exists()).isFalse();
   }
 
+  @Test
+  public void testDeleteOneLineFile() throws IOException, PatchFailedException {
+    Path oldFile = scratch.file("/root/oldfile", "bye, world");
+    Path patchFile =
+        scratch.file(
+            "/root/patchfile",
+            "--- a/oldfile",
+            "+++ /dev/null",
+            "@@ -1 +0,0 @@", // diff will produce such chunk header for one line file.
+            "-bye, world");
+    PatchUtil.apply(patchFile, 1, root);
+    assertThat(oldFile.exists()).isFalse();
+  }
+
   @Test
   public void testDeleteAllContentButNotFile() throws IOException, PatchFailedException {
     // If newfile is not /dev/null, we don't delete the file even it's empty after patching,