`xml.etree.ElementTree` — doesn't allow specifying fine-grained formatting controls

(Note: I already have a PR and this is a tracking issue.)

Enhancement

XML is maddening from a Git perspective, as if multiple tools will edit it, you'll get lots of lines in the diff that aren't needed.

For example:

diff --git a/sources/designspace/Besley.designspace b/sources/designspace/Besley.designspace
index d247944..eecb985 100644
--- a/sources/designspace/Besley.designspace
+++ b/sources/designspace/Besley.designspace
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8"?>
+<?xml version='1.0' encoding='UTF-8'?>

And:

diff --git a/sources/designspace/Besley.designspace b/sources/designspace/Besley.designspace
index d247944..9d570dd 100644
--- a/sources/designspace/Besley.designspace
+++ b/sources/designspace/Besley.designspace
@@ -10,15 +10,15 @@
       <map input="800" output="766"/>
       <map input="900" output="900"/>
     </axis>
-    <axis tag="wdth" name="Width" minimum="75" maximum="100" default="100"></axis>
+    <axis tag="wdth" name="Width" minimum="75" maximum="100" default="100" />
   </axes>
 
   <sources>
 
     <source filename="../ufo/Besley-Book.ufo" name="Besley Regular" familyname="Besley" stylename="Regular">
       <location>
-        <dimension name="Weight" xvalue="400"/>
-        <dimension name="Width" xvalue="100"/>
+        <dimension name="Weight" xvalue="400" />
+        <dimension name="Width" xvalue="100" />
       </location>
     </source>
 

There are likely other issues, but I only needed to solve these two.

首先审查 issue 中提到的现有 pull request，以及它所修改的 xml.etree.ElementTree 格式化行为。当调用方能够独立控制 XML 声明的引号和空元素格式，并且涵盖所示的两个示例时，工作即告完成。