update_file_list.sed

# Collapse all /foo/../ sequences in paths
s/(\/[^./]+){1}(\/\.\.){1}//g
# Collapse all /foo/bar/../../ sequences in paths
s/(\/[^./]+){2}(\/\.\.){2}//g
# Collapse all /foo/../ sequences in paths again
s/(\/[^./]+){1}(\/\.\.){1}//g
# Collect line following line like 'foo.o <ignore>: \'
/^\S+.o(\s+[^:]+)*:\s+\\$/N
# Extract object source file from line like 'foo.o <ignore>: \nfoo.c'
s/^\S+.o(\s+[^:]+)*:\s+\\\n\s*(\S+).*/\2/p
# Extract object source file from line like 'foo.o <ignore>: foo.c'
s/^\S+.o(\s+[^:]+)*:\s+(\S+).*/\2/p
# Extract dependency file from line like 'foo.h:'
s/^\s*([^/]\S+):\s*$/\1/p