[PATCH 0/9] Assorted fixes for `git config` (including the "empty sections" bug)

This patch series started out as a single patch trying to figure out what it takes to fix that annoying bug that has been reported several times over the years, where `git config --unset` would leave empty sections behind, and `git config --add` would not reuse them.

Little did I know that this would turn not only into a full patch to fix this issue, but into a full-blown series of nine patches.

The first patch is somewhat of a "while at it" bug fix that I first thought would be a lot more critical than it actually is: It really only affects config files that start with a section followed immediately (i.e. without a newline) by a one-letter boolean setting (i.e. without a `= <value>` part). So while it is a real bug fix, I doubt anybody ever got bitten by it.

Nonetheless, I would be confortable with this patch going into v2.17.0, even at this late stage. The final verdict is Junio's, of course.

The next swath of patches add some tests, and adjust one test about which I already complained at length yesterday, so I will spare you the same ordeal today. These fixes are pretty straight-forward, and I always try to keep my added tests as concise as possible, so please tell me if you find a way to make them smaller (without giving up readability and debuggability).

Finally, the interesting part, where I do two things, essentially (with preparatory steps for each thing):

1. I add the ability for `git config --unset/--unset-all` to detect that it
   can remove a section that has just become empty (see below for some more
   discussion of what I consider "become empty"), and

2. I add the ability for `git config [--add] key value` to re-use empty
   sections.

Note that the --unset/--unset-all part is the hairy one, and I would love it if people could concentrate on wrapping their heads around that function, and obviously tell me how I can change it to make it more readable (or even point out incorrect behavior).

Now, to the really important part: why does this patch series not conflict with my very early statements that we cannot simply remove empty sections because we may end up with stale comments?

Well, the patch in question takes pains to determine *iff* there are any comments surrounding, or included in, the section. If any are found: previous behavior. Under the assumption that the user edited the file, we keep it as intact as possible (see below for some argument against this). If no comments are found, and let's face it, this is probably *the* common case, as few people edit their config files by hand these days (neither should they because it is too easy to end up with an unparseable one), the now-empty section *is* removed.

So what is the argument against this extra care to detect comments? Well, if you have something like this:

	[section]
		; Here we comment about the variable called snarf
		snarf = froop

and we run `git config --unset section.snarf`, we end up with this config:

	[section]
		; Here we comment about the variable called snarf

which obviously does not make sense. However, that is already established behavior for quite a few years, and I do not even try to think of a way how this could be solved.

Johannes Schindelin (9):
  git_config_set: fix off-by-two
  t1300: rename it to reflect that `repo-config` was deprecated
  t1300: avoid relying on a bug
  t1300: remove unreasonable expectation from TODO
  t1300: `--unset-all` can leave an empty section behind (bug)
  git_config_set: simplify the way the section name is remembered
  git config --unset: remove empty sections (in normal situations)
  git_config_set: use do_config_from_file() directly
  git_config_set: reuse empty sections

 config.c                                    | 234 +++++++++++++++++++++++++---
 t/{t1300-repo-config.sh => t1300-config.sh} |  36 ++++-
 2 files changed, 250 insertions(+), 20 deletions(-)
 rename t/{t1300-repo-config.sh => t1300-config.sh} (98%)

base-commit: 03df4959472e7d4b5117bb72ac86e1e2bcf21723
Published-As: https://github.com/dscho/git/releases/tag/empty-config-section-v1
Fetch-It-Via: git fetch https://github.com/dscho/git empty-config-section-v1