Regularise use of repeats, tune (A/B/C etc.) markers and final bar. 1. Only show tune markers when a tune change is in the middle of a line. 2. Only show repeat starts |: if the repeat start is in the middle of a line. 3. Final bar end mark must be a thick line. The official rules for a repeat are that if there is no left repeat marker |: then the repeat starts at the previous double bar.

%abc
X:1
T:Shave the Donkey
M:4/4
S:Bacon (RD)
A:Bampton
O:English
R:Reel
P:A.(AB3)3.A
K:G
I:speed 300
P:A
|: "G" d2 B2 "D7" dcBA | "G" G2 g2 "C" e2 g2 |\
"G" d2 B2 "D7" dcBA | "G" G2 B2 G4 :|
P:B
|: "D7" A3 c "G" B2 d2 | "D7" A3 c "G"  B2 d2 |\
"D7" A3 c "C" c2 e2 | "D7" dcBA  "G" G4 :|