add documentation for writing config files

Replace TODO introduced in commit 9c3c22 with documentation
explaining Git config API functions for writing configuration
files.

Signed-off-by: Tanay Abhra <tanayabh@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-push: fix link in man page

Signed-off-by: Tony Finch <dot@dotat.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'ta/doc-config'

* ta/doc-config:
  add documentation for writing config files
Merge branch 'tf/maint-doc-push'

* tf/maint-doc-push:
  git-push: fix link in man page
Git 2.1.0-rc1

Signed-off-by: Junio C Hamano <gitster@pobox.com>
RelNotes: no more check_ref_format micro-optimization

Signed-off-by: Junio C Hamano <gitster@pobox.com>
various contrib: Fix links in man pages

Inspired by 2147fa7e (2014-07-31 git-push: fix link in man page),
I grepped through the whole tree searching for 'gitlink:' occurrences.

Signed-off-by: Stefan Beller <stefanbeller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Release notes: grammatical fixes

Signed-off-by: Marc Branchaud <marcnarc@xiplink.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'mb/relnotes-2.1'

* mb/relnotes-2.1:
  Release notes: grammatical fixes
  RelNotes: no more check_ref_format micro-optimization
diff: compare hashes to determine identical binary files

This is how builtin_diffstat does it, but I have a feeling
that it is buggy, and we need to be checking sha1_valid.
diff: only load binary files if we are going to diff them
diff_populate_filespec: convert size_only arg to bitfield

This will let us easily add more flags without disrupting
the existing callers. The DIFF_POPULATE_SIZE_ONLY flag
becomes flag "1", so any existing callers (e.g., in topics
in flight) that are not converted to use the macro will
still work.
diff_populate_filespec: add a PEEK option

This lets callers peek only at the first few kilobytes of
the buffer, which we can then sometimes use to avoid loading
large blobs.
enable diff-PEEKing

This works, but is way less fast than I would have hoped. It
turns my 16s "log -p" into 13s. Actually using gitattributes
turns it into 0.1s. Also, you have to tweak
core.bigfilethreshold to make it work, which is probably bad
(we would want to have different thresholds for reading and
writing).