Confusing error messages for branch errors

[jhclark]

Not sure how fixable this is, but the addition of anonymous branch points seems to have caused more confusing error messages. Since branch names currently can't begin with numbers, we get:

train_size=(TrainSize: 10k=10000 100k=100000 1M=1000000 5M=5425625)

results in:

ERROR: ERROR: line 17 column 34: An unquoted literal may not contain whitespace. If you meant to refer to a variable, you probably forgot the $ sign.
/phase1/jhclark/experiments/thesis/ar-nist2012.conf:17

If you quote it:

train_size=(TrainSize: 10k="10000" 100k="100000" 1M="1000000" 5M="5425625")

then you get:

ERROR: HARD ERROR: line 17 column 29: An unquoted literal may not contain a double quotation mark
/phase1/jhclark/experiments/thesis/ar-nist2012.conf:17

Both of these appear to be generated from trying to parse the whole mess as an anonymous branch point. Not sure what the right fix is, but these are rather confusing.

[dowobeha]

@jhclark Is this a problem?

[jhclark]

The general problem is: what happens when a branch name contains an unallowed character and can we provide an intuitive error message in that case?