Correct compiler warnings in fast-import.
Correct compiler warnings in fast-import.

Junio noticed these warnings/errors in fast-import when compiling
with `-Werror -ansi -pedantic`.  A few changes are to reduce compiler
warnings, while one (in cmd_merge) is a bug fix.

Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git