./koch runCI should set a custom NIMBLE_DIR to avoid interference; and should honor --nim

[timotheecour]

XDG_CONFIG_HOME= ./koch --nim:/pathto/nim runCI
runs some commands that sometimes ignore --nim flag eg:

nimble install -y --nimbleDir:build/deps zip

instead:

• NIMBLE_DIR should be set (maybe to a tmp dir)
• --nim should be honored, eg via NIM_CONF env var: allows passing in custom config before all others and apply to sub-processes nim-lang/RFCs#336

scratch below

NIMBLE_DIR=$HOME/.nimble_fake60 XDG_CONFIG_HOME= nimble install --nim:$nimb -y --nimbleDir:build/deps zip

[juancarlospaco]

I wonder if would be better adding support for "dotenv" file format to stdlib ?. 🤔
Would be like 300 lines at most and provide the "best practice" way to handle all those env vars.

[timotheecour]

yes, a module to parse dotenv file format (std/formats/dotenv ?) would be useful (refs https://hexdocs.pm/dotenvy/dotenv-file-format.html) and easy to implement (i've implemented this myself as well as the reverse direction from /pathto/bar/baz/foo.txt to $MYENVVAR/fbaz/oo.txt which is also very useful eg for generating less verbose log entries etc)

that said, setting NIMBLE_DIR for runCI can be done independently of that:)