config: teach "git -c" to recognize an empty stringjk/command-line-config-empty-string

In a config file, you can do:

  [foo]
  bar

to turn the "foo.bar" boolean flag on, and you can do:

  [foo]
  bar=

to set "foo.bar" to the empty string. However, git's "-c"
parameter treats both:

  git -c foo.bar

and

  git -c foo.bar=

as the boolean flag, and there is no way to set a variable
to the empty string. This patch enables the latter form to
do that.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 64da795aba..1557cd919d 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -429,6 +429,11 @@ example the following invocations are equivalent:
 	given will override values from configuration files.
 	The <name> is expected in the same format as listed by
 	'git config' (subkeys separated by dots).
++
+Note that omitting the `=` in `git -c foo.bar ...` is allowed and sets
+`foo.bar` to the boolean true value (just like `[foo]bar` would in a
+config file). Including the equals but with an empty value (like `git -c
+foo.bar= ...`) sets `foo.bar` to the empty string.
 
 --exec-path[=<path>]::
 	Path to wherever your core Git programs are installed.