git-pickaxe: -L /regexp/,/regexp/

git-pickaxe: -L /regexp/,/regexp/

With this change, you can specify the beginning and the ending
line of the range you wish to inspect with pattern matching.

For example, these are equivalent with the git.git sources:

    git pickaxe -L 7,21                       v1.4.0 -- commit.c
    git pickaxe -L '/^struct sort_node/,/^}/' v1.4.0 -- commit.c
    git pickaxe -L '7,/^}/'                   v1.4.0 -- commit.c
    git pickaxe -L '/^struct sort_node/,21'   v1.4.0 -- commit.c

Signed-off-by: Junio C Hamano <junkio@cox.net>