Center Align numbers right-ish

[th1000s]

There is no such thing as "Center Align" with discrete terminal cells. In
some cases a decision has to be made whether to use the left or the right
cell, e.g. when fitting one char into 4 cells: _X__ or __X_.

The format!() center/^ default is left, but when padding numbers these
are now aligned to the right if required. Strings remain left-aligned.

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I noticed this while adding line numbers to the blame output.

For my taste the center-right alignment of numbers looks better, see below and let me know what you think.

I think that makes a good default, otherwise extra format specifiers might be added, e.g.
"center left: {num:^<4} center right {num:^>4}"

string: │ 3  │     num: │  3 │
string: │ 4  │     num: │  4 │
string: │ 5  │     num: │  5 │
string: │ 6  │     num: │  6 │
string: │ 7  │     num: │  7 │
string: │ 8  │     num: │  8 │
string: │ 9  │     num: │  9 │
string: │ 10 │     num: │ 10 │
string: │ 11 │     num: │ 11 │
string: │ 12 │     num: │ 12 │
string: │ 13 │     num: │ 13 │
string: │ 94 │     num: │ 94 │
string: │ 95 │     num: │ 95 │
string: │ 96 │     num: │ 96 │
string: │ 97 │     num: │ 97 │
string: │ 98 │     num: │ 98 │
string: │ 99 │     num: │ 99 │
string: │100 │     num: │ 100│
string: │101 │     num: │ 101│
string: │102 │     num: │ 102│
string: │103 │     num: │ 103│
string: │104 │     num: │ 104│
string: │105 │     num: │ 105│
string: │106 │     num: │ 106│
string: │107 │     num: │ 107│
string: │108 │     num: │ 108│
string: │109 │     num: │ 109│
string: │110 │     num: │ 110│
string: │111 │     num: │ 111│
string: │998 │     num: │ 998│
string: │999 │     num: │ 999│
string: │1000│     num: │1000│

[dandavison]

Maybe say explicitly that this is 1 + floor(log10(n)) (if I got that right)

[th1000s]

Indeed. This specific log function was actually my original motivation add benchmarks to delta :)

[dandavison]

Excellent, I hope the test alterations weren't too painful!

[th1000s]

No, that was mostly sed -i 's,│ 1 │,│ 1 │,g' :)