[duckdb/#11727] - Tests fail because of missing version: is git required? needs documentation

[duckdblabs-bot]

See https://github.com/duckdb/duckdb/issues/11727

[carlopi]

From the original discussion, this is the logic to decide what version / hash to use in duckdb:

• if you specify OVERRIDE_GIT_DESCRIBE to be a formatted like the output of git describe --tags --long, for example for v0.10.2 it would be v0.10.2-0-g1601d94f94, that value is used to extract both the version, the dev-version, and the hash to be backed in both DuckDB libraries, binaries and extensions.
• if you specify OVERRIDE_GIT_DESCRIBE only partially, like if you provide only v0.10.2, the full git describe --tags --long-equivalent is reconstructed asking git the current commit, and that string is used as in part 1
• if you DO NOT specify OVERRIDE_GIT_DESCRIBE, AND git is present in the system, git describe --tags --long is computed by GIT and the output is used for further processing
• if you DO NOT specify OVERRIDE_GIT_DESCRIB, AND git is NOT available / functional, the string: v0.0.1-0-g0123456789 is used and a message is logged in the CMake output informing of this.

and should probably find some place in the docs building guide.

Also mentioning / stressing that python and git are optional dependency.