Auto-named column name counter never resets back to 'A'

[slinkeepie]

Test on current dev...

The auto-named column name counter never resets back to 'A' ...
Creating the first new sheet, col 0 will be named 'A', and any other auto-name col add action (e.g. addcol-incr) will step the letters up as expected, but start a new sheet and it won't start from 'A' for that sheet.

To observe:
Run open-new multiple times, only the first one will have its column named as 'A'

[frosencrantz]

I have been meaning to report this. Also, the naming is not undo-able, so if you undo and try to aadd the the column again the name will be different. This can cause issues for replayability for macros.

The code uses a generator function, that is global to the VisiData process, which causes it to always boldly go forward, never going back.

visidata/visidata/column.py

Lines 43 to 51 in 654eb87

	def _default_colnames():
	'A B C .. Z AA AB .. ZZ AAA .. to infinity'
	i=0
	while True:
	i += 1
	for x in itertools.product(string.ascii_uppercase, repeat=i):
	yield ''.join(x)
	default_colnames = _default_colnames()

[midichef]

Good point about the undo of naming! Thanks for mentioning it. I'd started on a fix that kept relying on a generator, and so would not fix undo. I'll change it to fix undo.