rebase doc: document rebase.useBuiltin

The rebase.useBuiltin variable introduced in 55071ea248 ("rebase: start implementing it as a builtin", 2018-08-07) was turned on by default in 5541bd5b8f ("rebase: default to using the builtin rebase", 2018-08-08), but had no documentation. Let's document it so that users who run into any stability issues with the C rewrite know there's an escape hatch[1], and make it clear that needing to turn off builtin rebase means you've found a bug in git. 1. https://public-inbox.org/git/87y39w1wc2.fsf@evledraar.gmail.com/ Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Ævar Arnfjörð Bjarmason committed Nov 14, 2018 at 09:15 UTC d8d0a546f04be2990d50425fe152af915bc3b82f
1 file changed +14
Documentation/config/rebase.txt
+14
@@ -1,3 +1,17 @@
1 +rebase.useBuiltin::
2 + Set to `false` to use the legacy shellscript implementation of
3 + linkgit:git-rebase[1]. Is `true` by default, which means use
4 + the built-in rewrite of it in C.
5 ++
6 +The C rewrite is first included with Git version 2.20. This option
7 +serves an an escape hatch to re-enable the legacy version in case any
8 +bugs are found in the rewrite. This option and the shellscript version
9 +of linkgit:git-rebase[1] will be removed in some future release.
10 ++
11 +If you find some reason to set this option to `false` other than
12 +one-off testing you should report the behavior difference as a bug in
13 +git.
14 +
15 rebase.stat::
16 Whether to show a diffstat of what changed upstream since the last
17 rebase. False by default.