Patch to add resume feature to scp

[Girish Venkatachalam]

Dear all,

I have enhanced scp to do the following.

1) Check the SHA1 checksums of the file fragments at the source and
destination and resume  file transfer from where it left off last time

2) If the file checksums match and size also matches, then the file is
assumed to be identical and skipped, the user is also informed of the
same

3) If the destination file size is larger than the source, it is
overwritten(conforms to prev behavior, the enhancement here being that
checksum computation is short circuited)

4) If the checksums do not match for the fragment, then the file is overwritten

5) All the above works well in recursive mode also, the identical
files are skipped, broken transfers resumed and all other times files
are transferred like before

6) One important feature of this enhancement is that if the same file
is not found at the destination , then the previous wire protocol is
preserved, thus there would be no version mismatch problem for fresh
transfers.


However these changes do necessitate a bump in the version number
IMHO. I could not think of any other way to solve this problem.

I will only be too glad to make whatever changes are necessary to
apply this patch to HEAD.

Hope you like this work. :-)

regards,
Girish