[9fans] plan 9 kernel history

[Russ Cox <russcox@gmail.com>]

A fairly complete history of the Plan 9 kernel is now
available at /n/sources/contrib/9hist.tar.gz, which is
also unpacked for browsing in /n/sources/contrib/9hist.
The data may be of interest to people studying the
evolution of software.

Each file (e.g., 9hist/carrera/main.c) is stored as a sequence
of ed scripts that can be run to create successive versions
of the file over time.  The show and showdiff scripts let you
inspect a particular file's history.  For example,

    cd /n/sources/contrib/9hist
    show carrera/main.c
    showdiff carrera/main.c 1999/1031
    show carrera/main.c 1999/1031
    showdiff carrera/main.c

There is a web version of the data at http://swtch.com/plan9history.
Aside from being GUIer, the presentation there is annotated
with comments about the various changes.

Thanks to Lucent and kernel authors past and present for
agreeing to publish the data.

Enjoy.
Russ