I pieced this together from other sources. Here's a sample file
app.plist that could be put on any server
to facilitate a re-install of an IPA
<plist version="1.0">
<dict>
<key>items</key>
<array>
<dict>
<key>assets</key>
<array>
<dict>
<key>kind</key>
<string>software-package</string>
<key>url</key>
<string>https://yourserver/yourapp.ipa</string>
</dict>
</array>
<key>metadata</key>
<dict>
<key>bundle-identifier</key>
<string>yourappname</string>
<key>bundle-version</key>
<string>4.0</string>
<key>kind</key>
<string>software</string>
<key>subtitle</key>
<string>41A472</string>
<key>title</key>
<string>yourappname</string>
</dict>
</dict>
</array>
</dict>
</plist>
The one gotcha is that the server protocol must be https:
Part 2 is the actual URL you feed to safari or another browser. It's convenient to make a trampoline
app.htmlthat looks like this:
<script>
location.href='itms-services://?action=download-manifest&url=https://yourserver/app.plist';
</script>
The other gotcha is that this will only work for a debug build, due to signing issues I suppose, but at least
old debug builds can be reinstated for comparison with current ones.