`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.

Start by reviewing the existing pull request mentioned in the issue and the xml.etree.ElementTree formatting behavior it changes. The work is complete when callers can control the XML declaration quoting and empty-element formatting independently, with coverage for both examples shown.