*goredo* redo implementation on pure Go

OVERVIEW                                               *goredo-overview*

This is pure Go implementation of DJB's redo (http://cr.yp.to/redo.html)
build system proposal. Originally it was just a rewrite of redo-c
(https://github.com/leahneukirchen/redo-c), but later most features of
apenwarr/redo (https://redo.readthedocs.io/en/latest/) were also
implemented. Why yet another implementation? It is feature full and has
better performance comparing to shell and Python implementation.
goredo is free software: see the file COPYING for copying conditions.

INSTALL                                                 *goredo-install*

Either: >
    $ go get go.cypherpunks.ru/goredo
    $ goredo -symlinks
    $ export PATH=`pwd`:$PATH
or: >
    $ git clone git://git.cypherpunks.ru/goredo.git
    $ cd goredo
    $ go build
    $ ./goredo -symlinks
    $ export PATH=`pwd`:$PATH
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NOTES                                                     *goredo-notes*

* "all" target is used by default
* stdout is always captured, but no target is created if it was empty
* empty targets are considered always out of date
* .do's arguments are relative paths
* .do search goes up to / by default, but can be limited with either
  REDO_TOP_DIR environment variable, or by having .redo/top file in it
* target's completion messages are written after they finish
* executable .do is run as is, non-executable is run with /bin/sh -e[x]
* tracing (-x) can be done only for non-executable .do

FEATURES                                               *goredo-features*

* explicit useful and convenient checks from apenwarr/redo:
    * check that $1 was not touched during .do execution
    * check that stdout and $3 are not written simultaneously
    * check that generated target was not modified "externally" outside
      the redo, preventing its overwriting, but continuing the build
* targets, dependency information and their directories are explicitly
  synced (can be disabled, should work faster)
* file's change is detected by comparing its ctime and BLAKE2b hash
* files creation is umask-friendly (unlike mkstemp() used in redo-c)
* parallel build with jobs limit, optionally in infinite mode
* coloured messages (can be disabled)
* verbose debug messages, including out-of-date determination, PIDs,
  lock and jobserver acquirings/releases
* displaying of each target's execution time
* each target's stderr can be displayed with the PID
* optional statusline with currently running/waiting/done jobs
* target's stderr can be stored on the disk with TAI64N timestamp
  prefixes for each line. To convert them to localtime you can use either
  tai64nlocal utility from daemontools (http://cr.yp.to/daemontools.html)
  or make a symlink, to use built-in slower decoder: >
    $ ln -s goredo tai64nlocal
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COMMANDS                                               *goredo-commands*

* redo-ifchange, redo-ifcreate, redo-always (useful with redo-stamp)
* redo -- same as redo-ifchange, but forcefully and *sequentially* run
  specified targets
* redo-log -- display TAI64N timestamped last stderr of the target
* redo-stamp -- record stamp dependency. Nothing more, just dummy
* redo-cleanup -- removes either temporary, log files, or everything
  related to goredo
* redo-whichdo -- .do search paths for specified target (similar to
  apenwarr/redo): >
    $ redo-whichdo x/y/a.b.o
    x/y/a.b.o.do
    x/y/default.b.o.do
    x/y/default.o.do
    x/y/default.do
    x/default.b.o.do
    x/default.o.do
    x/default.do
    default.b.o.do
    default.o.do
    default.do
    ../default.b.o.do
    ../default.o.do
* redo-dot -- dependency DOT graph generator. For example to visualize
  your dependencies with GraphViz: >
    $ redo target [...] # to assure that .redo is filled up
    $ redo-dot target [...] > whatever.dot
    $ dot -Tpng whatever.dot > whatever.png # possibly add -Gsplines=ortho
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FAQ                                                         *goredo-faq*

    Hashing and stamping~

All targets are checksummed if their ctime differs from the previous
ones. apenwarr/redo gives many reasons why every time checksumming is
bad, but in my opinion in practice all of his reasons do not apply.

* Aggregate targets and willing to be out-of-date ones just must not
  produce empty output files. apenwarr/*, redo-c and goredo
  implementations consider non existing file as an out-of-date target
* If you really wish to produce an empty target file, just: touch $3

DJB's proposal with both stdout and $3 gives that ability to control
your desired behaviour. Those who does not capture stdout -- failed.
Those who creates an empty file if no stdout was written -- failed.

redo is a tool for helping people. Literally all targets can be safely
"redo-stamp < $3"-ed, reducing false positive out-of-dates. Of course,
with the correct working with stdout/$3 and placing necessary results in
$3, instead of just silently feeding them in redo-stamp.

redo implementations are already automatically records -ifchange on .do
files and -ifcreate on non-existing .do files. So why they can not
record redo-stamp the same way implicitly? No, Zen of Python does not
applicable there, because -ifchange/-ifcreate contradict it already.

Modern cryptographic hash algorithms and CPUs are so fast, that even all
read and writes to or from hard drive arrays can be easily checksummed
and transparently compressed, as ZFS with LZ4 and Skein/BLAKE[23]
algorithms demonstrate us.

goredo includes redo-stamp, that really records the stamp in the .dep
file, but it does not play any role later. It is stayed just for
compatibility.

    Removed .do can lead to permanent errors of its non existence~

That is true, because dependency on it was recorded previously. Is it
safe to assume that .do-less target now is an ordinary source-file? I
have no confidence in such behaviour. So it is user's decision how to
deal with it, probably it was just his inaccuracy mistake. If you really
want to get rid of that dependency knowledge for foo/bar target, then
just remove foo/.redo/bar.dep.

STATE                                                     *goredo-state*

Dependency and build state is kept inside .redo subdirectory in each
directory touched related the build. Each corresponding target has its
own, recreated with every rebuild, .dep file. It is recfile
(https://www.gnu.org/software/recutils/), that could have various
dependency information (dep.rec with the schema included): >

    Build: 80143f04-bfff-4673-950c-081d712f573d

    Type: ifcreate
    Target: foo.o.do

    Type: ifchange
    Target: default.o.do
    Ctime: 1605721341.253305000
    Hash: f4929732f96f11e6d4ebe94536b5edef426d00ed0146853e37a87f4295e18eda

    Type: always

    Type: stamp
    Hash: 5bbdf635932cb16b9127e69b6f3872577efed338f0a4ab6f2c7ca3df6ce50cc9
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LICENCE~

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

 vim: filetype=help