checksums: support all OpenSSL EVP digests

Add option "-c digest" to use any of supported EVP message digests
inplace of insecure MD5. This generates checksum files named by the digest
by default, e.g .SHA256.CHECKSUMS

Rename md5.c to checksum.c
Rename md5_* functions to csum_* functions
Rename MD5* variables to Csum* variables

For backwards compatibility -m translates to -c md5
The "-M filename" option to rename the checksums file remains untouched

Author: mmatuska

PORTING

@@ -21,10 +21,10 @@ $DragonFly: src/bin/cpdup/PORTING,v 1.2 2008/04/11 17:33:11 dillon Exp $
     #!/bin/csh
     #
     cd cpdup
-    rm -f md5.c
+    rm -f checksum.c
     rm -f *.o
-    cc -D__unused= -D_GNU_SOURCE -D__USE_FILE_OFFSET64 -DNOMD5 *.c -c
-    cc -D__unused= -D_GNU_SOURCE -D__USE_FILE_OFFSET64 -DNOMD5 *.o -o ~/bin/cpdup
+    cc -D__unused= -D_GNU_SOURCE -D__USE_FILE_OFFSET64 -DNOCHECKSUM *.c -c
+    cc -D__unused= -D_GNU_SOURCE -D__USE_FILE_OFFSET64 -DNOCHECKSUM *.o -o ~/bin/cpdup
 
     BACKUP SCRIPT MODIFICATIONS - you will almost certainly have to adjust
     the do_cleanup script to extract the proper field(s) from the df output.

cpdup.1

@@ -12,6 +12,7 @@
 .Nm
 .Op Fl C
 .Op Fl v Ns Op Cm v Ns Op Cm v
+.Op Fl c
 .Op Fl d
 .Op Fl n
 .Op Fl u
@@ -73,6 +74,27 @@ modifications made to the destination.
 .Fl vvv
 will cause all files and directories to be reported whether or not
 modifications are made.
+.It Fl c Ar digest
+Generate and maintain a checksum file using the specified message
+.Ar digest
+called
+.Pa \&.DIGEST.CHECKSUMS
+in each directory on the source where
+.Pa DIGEST
+is replaced by the upperscale name of the message digest used.
+An alternate file name may be specified with the
+.Fl M Ar file
+option. Supported are all localy available OpenSSL
+.Xr EVP 7
+message digests, e.g. md5, rmd160, sha1, sha256 or sha512.
+A checksum check is done on each file of the destination when the destination
+appears to be the same as the source.  If the check fails,
+the source is recopied to the destination.  When you specify a destination
+directory, the checksum file is only updated as needed and may not be updated
+even if modifications are made to a source file.  If you do not specify a
+destination directory the
+.Nm
+command forcefully regenerates the checksum for every file in the source.
 .It Fl d
 Print directories as they are being traversed.
 Useful to watch the progress;
@@ -120,21 +142,14 @@ Quiet operation.
 .It Fl o
 Do not remove any files, just overwrite/add.
 .It Fl m
-Generate and maintain a MD5 checkfile called
-.Pa \&.MD5.CHECKSUMS
-in each directory on the source
-and do an MD5 check on each file of the destination when the destination
-appears to be the same as the source.  If the check fails,
-the source is recopied to the destination.  When you specify a destination
-directory, the MD5 checkfile is only updated as needed and may not be updated
-even if modifications are made to a source file.  If you do not specify a
-destination directory the
-.Nm
-command forcefully regenerates the MD5 checkfile for every file in the source.
-.It Fl M Ar file
 Works the same as
-.Fl m
-but allows you to specify the name of the MD5 checkfile.
+.Fl c Ar md5
+for compatibility purposes
+.It Fl M Ar file
+allows you to specify the name of the checksum file generated by options
+.Fl c
+or
+.Fl m.
 .It Fl H Ar path
 .Nm
 will create a hardlink from a file found under