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
update-index: add --clear option

This just discards existing entries from the index, which
can be useful if you are rewriting all entries with
"--index-info" or similar.
docs/filter-branch: clean up newsubdir example

Over the years, this simple example has ended up quite hard
to read because of the number of special cases that must be
handled. Let's simplify it a bit:

  1. Use the new "index-info --clear" to avoid the need for
     a temporary index.

  2. Use "-z" and "perl -0" to avoid dealing with quoting
     issues. As a bonus, using perl means that "\t" will
     work consistently in regexps (the previous example
     using sed was reported to fail on OS X).

  3. Change the indentation to keep one logical unit per
     line and avoid extra backslash-escaping.