I cannot find the source code for spring-boot-2.7.12.jar. I can find versions close to 2.7.12.
I downloaded spring-boot-2.7.12.jar from Maven Central, and I've confirmed that the Implementation-Version in MANIFEST.MF is "2.7.12".
I've cloned the spring-boot github repo, and I cannot find what I can identify as 2.7.12 release sources.
There's no tag that looks like "v2.7.12" (it seems that the Spring Buildmaster stopped tagging releases after V2.3.0.M4 in April of 2020--not a criticism, just an observation).
Looking in gradle.properties, the "2.7.x" branch only seems to have a version marked "2.7.12-SNAPSHOT". Since 2.3.1, version in gradle.properties always has the word "SNAPSHOT" in it.
The only git log messages for the 2.7 version family either mention merging the 2.7.x branch into another branch, or the reference the start of a SNAPSHOT version.
I was expecting to find a tag or branch with the string "2.7.12" in it, and/or a commit in which I could find the literal string "2.7.12" without "-SNAPSHOT" appended.