initdb's -c option behaves wrong way?

Hello.

I noticed that -c option of initdb behaves in an unexpected
manner. Identical variable names with variations in letter casing are
treated as distinct variables.

$ initdb -cwork_mem=100 -cWORK_MEM=1000 -cWork_mem=2000
...
$ grep -i 'work_mem ' $PGDATA/postgresql.conf
work_mem = 100 # min 64kB
#maintenance_work_mem = 64MB # min 1MB
#autovacuum_work_mem = -1 # min 1MB, or -1 to use maintenance_work_mem
#logical_decoding_work_mem = 64MB # min 64kB
WORK_MEM = 1000
Work_mem = 2000

The original intention was apparently to overwrite the existing
line. Furthermore, I surmise that preserving the original letter
casing is preferable.

Attached is a patch to address this issue. To retrieve the variable
name from the existing line, the code is slightly restructured.
Alternatively, should we just down-case the provided variable names?

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center