hgweb: discard Content-Type header for 304 responses (issue5844)
A side-effect of 98baf8dea553 was that hgwebdir always sets a global
default for the Content-Type header. HTTP 304 responses don't allow
the Content-Type header. So a side-effect of this change was that
HTTP 304 responses served via hgwebdir resulted in a ProgrammingError
being raised.
This commit teaches our 304 response issuing code to drop the
Content-Type header.
Differential Revision: https://phab.mercurial-scm.org/D3435
$ hg init
$ $PYTHON -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
$ hg ci -Ama -d '1 0'
adding a
$ echo clean diff >> a
$ hg ci -mb -d '2 0'
$ hg diff -r0 -r1
diff -r 107ba6f817b5 -r 310ce7989cdc a
--- a/a Thu Jan 01 00:00:01 1970 +0000
+++ b/a Thu Jan 01 00:00:02 1970 +0000
@@ -1,2 +1,3 @@
confuse str.splitlines
embedded\r (no-eol) (esc)
newline
+clean diff