Closes:#883340.
* When quilt fixup fails because of discrepancies, print a
git diff rune which will show them. Closes:#865446.
+ * When fetch or push wants git fetch (other than in a situation where it
+ happes to be a noop) but --dry-run was specified, fail with an
+ explanation, rather than looping with a false coplaint about git
+ fetch. Closes:#871317.
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