This is somewhat offtopic but this list is the best-informed crowd on diff/xdelta matters so here I am, abusing your attention... I am working on an "incremental content" feature for Moodle - and my plan is to serve pre-computed "patchfiles" based on the xdelta utility to the client systems. Now, I need to provide a wrapper that concats the deltas from the xdelta utility with a more verbose header - akin to the header in git's unified diff output. This is because the xdelta utility only handles one file delta at a time - the file is a pure delta (prefaced with a SHA1 of the file it applies to, IIRC). (From xdelta I like that it's one-way-only, and compressed internally -- thus saving a lot of space on large changes. There are small statically linked binaries for windows, osx and linux. I did consider using git's own diffs, but it involves significantly more work, and portability to Win32 is still green for the wide distribution this project is expecting.) So my question is what is a good format for the header? My thinking sofar: - have a prefix to scan for, such as "xdelta" at the beginning of the file, or after a newline/whitespace - keep the <fromsha1> <tosha1> line - \0 delimited filenames - filenames as ambiguous bag'o'bytes or utf-8? (should we have another flamewar on this? ;-) ) - keep file modes and perhaps support copy/move headers - keep a/ b/ prefixes? - last line in the header is length: <length-in-bytes>, followed by a newline and the xdelta itself - one or more newlines follow the end of the xdelta if there is another header coming Something along the lines of xdelta d065883..74cd8e5 100644 a/foo.zip\0 b/foo.zip\0 length 1024 <1024 bytes of xdelta data> xdelta d065883..74cd8e5 100644 a/bar.zip\0 b/bar.zip\0 length 92312 <92312 bytes xdelta data>EOF --- Would the above work as a reasonably solid patch header format? Is there something else I should be using instead of rolling my own? If there isn't a more suitable tool, and I'm hoping to come up with something unambiguous and reliable that is generally useful. [ I have to confess, it came as a bit of a surprise that xdelta didn't support this out of the box. Haven't seen any existing wrapper for it that covers this either. ] As a kludge I could tar both sides and xdelta across the tars, but it is wasteful, and an xdelta-based diff/patch that can handle multiple files does seem useful. And I don't know how stable the output of tar is (wrt file ordering for example). TIA for any feedback :-) m -- - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
