strange behaviour on file with ':' in its name

[Louis-David Mitterrand]

Using 3.0.5 I can't send a file with ':' in its name in the current
directory without prefixing it with ./

delos% touch file:ext

delos% rsync -avP file:ext sylla:/home/ldm
The source and destination cannot both be remote.
rsync error: syntax or usage error (code 1) at main.c(1154) [receiver=3.0.5]

delos:~% rsync -avP "file:ext" sylla:/home/ldm
The source and destination cannot both be remote.
rsync error: syntax or usage error (code 1) at main.c(1154) [receiver=3.0.5]

delos:~% rsync -avP file\:ext sylla:/home/ldm 
The source and destination cannot both be remote.
rsync error: syntax or usage error (code 1) at main.c(1154) [receiver=3.0.5]

delos:~% rsync -avP ./file:ext sylla:/home/ldm
sending incremental file list
file:ext
           0 100%    0.00kB/s    0:00:00 (xfer#1, to-check=0/1)
sent 83 bytes  received 31 bytes  228.00 bytes/sec
total size is 0  speedup is 0.00

delos:~% touch file.ext  

delos:~% rsync -aP file.ext sylla:/home/ldm
sending incremental file list
file.ext
           0 100%    0.00kB/s    0:00:00 (xfer#1, to-check=0/1)
sent 83 bytes  received 31 bytes  76.00 bytes/sec
total size is 0  speedup is 0.00