Verify Content-Type from smart HTTP servers

Before parsing a suspected smart-HTTP response verify the returned
Content-Type matches the standard. This protects a client from
attempting to process a payload that smells like a smart-HTTP
server response.

JGit has been doing this check on all responses since the dawn of
time. I mistakenly failed to include it in git-core when smart HTTP
was introduced. At the time I didn't know how to get the Content-Type
from libcurl. I punted, meant to circle back and fix this, and just
plain forgot about it.

Signed-off-by: Shawn Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t5551: fix expected error output

We should probably get rid of the check of message instead, but in
the meantime this should do.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
http_request: reset "type" strbuf before adding

Callers may pass us a strbuf which we use to record the
content-type of the response. However, we simply appended to
it rather than overwriting its contents, meaning that cruft
in the strbuf gave us a bogus type. E.g., the multiple
requests triggered by http_request could yield a type like
"text/plainapplication/x-git-receive-pack-advertisement".

Reported-by: Michael Schubert <mschub@elegosoft.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
user-manual: Fix 'both: so' -> 'both; so' typo

The clause "so `git log ...` will return no commits..." is
independent, not a description of "both", so a semicolon is more
appropriate.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'sp/smart-http-content-type-check'

The smart HTTP clients forgot to verify the content-type that comes
back from the server side to make sure that the request is being
handled properly.

* sp/smart-http-content-type-check:
  http_request: reset "type" strbuf before adding
  t5551: fix expected error output
  Verify Content-Type from smart HTTP servers
user-manual: Fix 'http' -> 'HTTP' typos

HTTP is an acronym which has not (yet) made the transition to word
status (unlike "laser", probably because lasers are inherently cooler
than HTTP ;).

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
user-manual: Fix 'you - Git' -> 'you--Git' typo

Use an em-dash, not a hyphen, to join these clauses.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
user-manual: Rewrite git-gc section for automatic packing

This should have happened back in 2007, when `git gc` learned about
auto (e9831e8, git-gc --auto: add documentation, 2007-09-17).

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'maint'

* maint:
  user-manual: Rewrite git-gc section for automatic packing
  user-manual: Fix 'you - Git' -> 'you--Git' typo
  user-manual: Fix 'http' -> 'HTTP' typos
  user-manual: Fix 'both: so' -> 'both; so' typo
Update draft release notes to 1.8.2

Signed-off-by: Junio C Hamano <gitster@pobox.com>