Difference between the format and db/format files in a Subversion repository

The format file contains information about Subversion repository format, while db/format holds information about Subversion Repository File System (FS) format.

Repository format number:

• Formats 0, 1 and 2 were pre-1.0.
• Format 3 was current for 1.0 through to 1.3.
• Format 4 was an abortive experiment during the development of the locking feature in the lead up to 1.2.
• Format 5 was new in 1.4, and is the first format which may contain BDB or FSFS filesystems with a FS format other than 1, since prior formats are accepted by some versions of Subversion which do not pay attention to the FS format number.

FSFS format number:

• Format 1, understood by Subversion 1.1+
• Format 2, understood by Subversion 1.4+, introduced support for svn diff version 1
• Format 3, understood by Subversion 1.5+, sharded layout and storing merge tracking information
• Format 4, understood by Subversion 1.6+, represention sharing and repository packing
• Format 5 was added during Subversion 1.7 development, but was removed before 1.7.0 final release
• Format 6, understood by Subversion 1.8+, revision properties packing
• Format 7, understood by Subversion 1.9+, performance related changes
• Format 8, understood by Subversion 1.10+, LZ4 compression