How do I determine the SVN working copy layout version?

From Stack Overflow question Find out SVN working copy version (1.7 or 1.8):

One can use sqlite3 .svn/wc.db "PRAGMA user_version" on SVN 1.7 or later (or od -An -j63 -N1 -t dC .svn/wc.db if you only have the SQLite 3.0 libraries, YMMV).

If .svn/format exists, then read the number in it:

• Version 7 is SVN 1.3
• Version 8 is SVN 1.4
• Version 9 is SVN 1.5

If .svn/format doesn't exist then the version number is on the first line in .svn/entries:

• Version 10 is SVN 1.6
• Version 12 is SVN 1.7

Subversion 1.6 was the first one not to use .svn/format. Version 7 and older used XML-based .svn/entries file, newer versions use less verbose line-based file format.

Since Subversion 1.7 the version number is stored in the .svn/wc.db SQLite database in the "user_version" field. So even though .svn/format is bumped to version 12 the actual format version is 29 and future versions may not update .svn/format anymore. To obtain the version number from .svn/wc.db there are two methods:

1. if you have sqlite3 in your path, sqlite3 .svn/wc.db "PRAGMA user_version"
2. if you DO NOT have sqlite3 in your path, open .svn/wc.db in a hex editor and read the DWORD at offset 0x3c

All the format version numbers are described in wc.h along with the version numbers of respective Subversion releases.