gitweb: clarify search results page when no matching commit found

gitweb: clarify search results page when no matching commit found

When searching commits for a string that never occurs, the results
page looks something like this:

	projects / foo.git / search                                 \o/
	summary | ... | tree          [commit] search: [ kfjdkas ] [ ]re
	first ⋅ prev ⋅ next

	Merge branch 'maint'

	Foo: a demonstration project

Without a list of hits to compare it to, the header describing the
commit named by the hash parameter (usually HEAD) may itself look
like a hit.  Add some text (“No match.”) to replace the empty
list of hits and avoid this confusion.

While at it, remove some nearby dead code, left behind from a
simplification a few years ago (v1.5.4-rc0~276^2~4, 2007-11-01).

Noticed-by: Erick Mattos <redacted>
Signed-off-by: Jonathan Nieder <redacted>
Acked-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>