Strip out unnecessary lines from the patch files

Author: j-f1

Patches/CSSOM.patch

@@ -1,5 +1,3 @@
-diff --git a/Sources/CSSOM/Generated.swift b/Sources/CSSOM/Generated.swift
-index 16a452b..1242f02 100644
 --- a/Sources/CSSOM/Generated.swift
 +++ b/Sources/CSSOM/Generated.swift
 @@ -378,7 +378,8 @@ public class CSSColorValue: CSSStyleValue {

Patches/DOM.patch

@@ -1,5 +1,3 @@
-diff --git a/Sources/DOM/Generated.swift b/Sources/DOM/Generated.swift
-index 1f45705..d5e36dd 100644
 --- a/Sources/DOM/Generated.swift
 +++ b/Sources/DOM/Generated.swift
 @@ -1005,8 +1005,15 @@ public class BeforeUnloadEvent: Event {

Patches/SVG.patch

@@ -1,5 +1,3 @@
-diff --git a/Sources/SVG/Generated.swift b/Sources/SVG/Generated.swift
-index 287fe12..5c83d7e 100644
 --- a/Sources/SVG/Generated.swift
 +++ b/Sources/SVG/Generated.swift
 @@ -544,14 +544,16 @@ public class SVGElement: Element, GlobalEventHandlers, DocumentAndElementEventHa

Patches/WebAudio.patch

@@ -1,5 +1,3 @@
-diff --git a/Sources/WebAudio/Generated.swift b/Sources/WebAudio/Generated.swift
-index fc5553f..590831f 100644
 --- a/Sources/WebAudio/Generated.swift
 +++ b/Sources/WebAudio/Generated.swift
 @@ -195,7 +195,8 @@ public class AudioBufferSourceNode: AudioScheduledSourceNode {

script/generate-patch

@@ -8,9 +8,13 @@ if [ $# -ne 1 ]; then
 fi
 
 FILE=Sources/$1/Generated.swift
+NEW_HEADER=$(cat <<EOF
+--- a/$FILE
++++ b/$FILE
+EOF)
 
 cp $FILE $FILE.modified
 swift run WebIDLToSwift --no-patch
-git diff --no-ext-diff --no-index $FILE $FILE.modified | sed s/.modified//g > Patches/$1.patch
+git diff --no-ext-diff --no-index $FILE $FILE.modified | tail -n +5 | sed "s/^/$NEW_HEADER/" | sed 's/[[:space:]]*$//'
 swift run WebIDLToSwift
 rm $FILE.modified