migration-5.2: document BB_CURRENT_MC default value change

After commit 0fa0d8d764bb ("cooker/cache: Drop mc 'default' string
value") in Bitbake, the default value of BB_CURRENT_MC was changed from
"default" to an empty string. Document it.

(From yocto-docs rev: efbd8fa30a5cc42d5243aa87e00e2d92cb265adb)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/documentation/migration-guides/migration-5.2.rst b/documentation/migration-guides/migration-5.2.rst
index e9de6910e1..a60e3e9a80 100644
--- a/documentation/migration-guides/migration-5.2.rst
+++ b/documentation/migration-guides/migration-5.2.rst
@@ -94,6 +94,17 @@ systemd changes
    not for socket files).
    Now all service files must be explicitly added to :term:`FILES`.
 
+Multiconfig changes
+~~~~~~~~~~~~~~~~~~~
+
+The value of ``BB_CURRENT_MC`` was changed from ``default`` to an empty string
+for the default multiconfig configuration to avoid needing to map the values
+within BitBake. This was already not happening in some cases so this fixes
+some obscure bugs.
+
+Any logic based on ``BB_CURRENT_MC`` equalling to ``default`` by default should
+be changed to be equal to an empty string.
+
 Recipe changes
 ~~~~~~~~~~~~~~