From 7596fab0a4d9cd52e2e2c03a816a4b34f029e7e0 Mon Sep 17 00:00:00 2001
From: Micah Young <myoung@pivotal.io>
Date: Wed, 18 Sep 2019 09:40:35 -0400
Subject: [PATCH 1/2] Adds api to buildpack.toml schema

Signed-off-by: Micah Young <myoung@pivotal.io>
Signed-off-by: Emily Casey <ecasey@pivotal.io>
---
 buildpack.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/buildpack.md b/buildpack.md
index fb383ef7..c46f3a70 100644
--- a/buildpack.md
+++ b/buildpack.md
@@ -937,6 +937,8 @@ For a given layer, the buildpack MAY specify:
 ### buildpack.toml (TOML)
 
 ```toml
+api = "<buildpack api>"
+
 [buildpack]
 id = "<buildpack ID>"
 name = "<buildpack name>"
@@ -967,6 +969,8 @@ The buildpack ID:
 
 If an `order` is specified, then `stacks` MUST NOT be specified.
 
+Buildpack API MUST be in form `<major>.<minor>` and describe the implemented buildpack API. When `<major>` is `0`, this buildpack is only compatible with lifecycles implementing that exact buildpack API. When `<major>` is greater than `0`, this buildpack is compatible with lifecycles implementing buildpack API `<major>.<minor>`, where `<major>` equals the `<major>` of the buildpack and `<minor>` is greater than or equal to that of the buildpack.
+
 #### Buildpack Implementations
 
 A buildpack descriptor that specifies `stacks` MUST describe a buildpack that implements the [Buildpack Interface](#buildpack-interface).

From 5fc5e3b212b9ff4ac80e292e15f6196f17b6cd7e Mon Sep 17 00:00:00 2001
From: Emily Casey <ecasey@pivotal.io>
Date: Thu, 19 Sep 2019 09:16:51 -0400
Subject: [PATCH 2/2] Allow buildpack api to imply a minor of 0 by omission

Signed-off-by: Emily Casey <ecasey@pivotal.io>
---
 buildpack.md | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/buildpack.md b/buildpack.md
index c46f3a70..4781ca9d 100644
--- a/buildpack.md
+++ b/buildpack.md
@@ -969,7 +969,12 @@ The buildpack ID:
 
 If an `order` is specified, then `stacks` MUST NOT be specified.
 
-Buildpack API MUST be in form `<major>.<minor>` and describe the implemented buildpack API. When `<major>` is `0`, this buildpack is only compatible with lifecycles implementing that exact buildpack API. When `<major>` is greater than `0`, this buildpack is compatible with lifecycles implementing buildpack API `<major>.<minor>`, where `<major>` equals the `<major>` of the buildpack and `<minor>` is greater than or equal to that of the buildpack.
+The buildpack API:
+ - MUST be in form `<major>.<minor>` or `<major>`, where `<major>` is equivalent to `<major>.0`
+ - MUST describe the implemented buildpack API.
+ - SHALL indicate compatibility with a given lifecycle according to the following rules:
+    - When `<major>` is `0`, the buildpack is only compatible with lifecycles implementing that exact buildpack API.
+    - When `<major>` is greater than `0`, the buildpack is only compatible with lifecycles implementing buildpack API `<major>.<minor>`, where `<major>` of the lifecycle equals `<major>` of the buildpack and `<minor>` of the lifecycle is greater than or equal to `<minor>` of the buildpack.
 
 #### Buildpack Implementations