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Directory reorg: move code into redo/, generate binaries in bin/.

Browse source 
It's time to start preparing for a version of redo that doesn't work
unless we build it first (because it will rely on C modules, and
eventually be rewritten in C altogether).

To get rolling, remove the old-style symlinks to the main programs, and
rename those programs from redo-*.py to redo/cmd_*.py.  We'll also move
all library functions into the redo/ dir, which is a more python-style
naming convention.

Previously, install.do was generating wrappers for installing in
/usr/bin, which extend sys.path and then import+run the right file.
This made "installed" redo work quite differently from running redo
inside its source tree.  Instead, let's always generate the wrappers in
bin/, and not make anything executable except those wrappers.

Since we're generating wrappers anyway, let's actually auto-detect the
right version of python for the running system; distros can't seem to
agree on what to call their python2 binaries (sigh). We'll fill in the
right #! shebang lines.  Since we're doing that, we can stop using
/usr/bin/env, which will a) make things slightly faster, and b) let us
use "python -S", which tells python not to load a bunch of extra crap
we're not using, thus improving startup times.

Annoyingly, we now have to build redo using minimal/do, then run the
tests using bin/redo.  To make this less annoying, we add a toplevel
./do script that knows the right steps, and a Makefile (whee!) for
people who are used to typing 'make' and 'make test' and 'make clean'.
This commit is contained in:
Avery Pennarun 2018-12-03 21:39:15 -05:00
commit f6fe00db5c
140 changed files with 256 additions and 99 deletions
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Documentation/redo.md
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# NAME
redo - rebuild target files when source files have changed
# SYNOPSIS
redo [options...] [targets...]
# DESCRIPTION
redo is a simple yet powerful tool for rebuilding target
files, and any of their dependencies, based on a set of
rules. The rules are encoded in simple `sh`(1) scripts
called '.do scripts.'
redo supports GNU `make`(1)-style parallel builds using the
`-j` option; in fact, redo's parallel jobserver is compatible
with GNU Make, so redo and make can share build tokens with
each other. redo can call a sub-make (eg. to build a
subproject that uses Makefiles) or vice versa (eg. if a
make-based project needs to build a redo-based subproject).
Unlike make, redo does not have any special syntax of its
own; each *target* is built by running a .do file, which is
simply a shell script that redo executes for you with a
particular environment and command-line arguments.
If no *targets* are specified, redo pretends you specified
exactly one target named `all`.
Note that redo *always* rebuilds the given targets
(although it may skip rebuilding the targets' dependencies
if they are up to date). If you only want to rebuild
targets that are not up to date, use `redo-ifchange`(1)
instead.
A .do script can call redo recursively to build its
dependencies.
To avoid confusion caused by multiple programs trying to
use the terminal, inside .do scripts, stdin is normally
redirected to /dev/null. The only exception is if the `-j`
option is *not* given and `--no-log` is used.
# OPTIONS
-j, --jobs=*maxjobs*
: execute at most *maxjobs* .do scripts in parallel. The
default value is 1.
-d, --debug
: print dependency checks as they happen. You can use
this to figure out why a particular target is/isn't being
rebuilt when your .do script calls it using
`redo-ifchange`.
-v, --verbose
: pass the -v option to /bin/sh when executing scripts.
This normally causes the shell to echo the .do script lines
to stderr as it reads them. Most shells will print the
exact source line (eg. `echo $3`) and not the
substituted value of variables (eg. `echo
mytarget.redo.tmp`).
-x, --xtrace
: pass the -x option to /bin/sh when executing scripts.
This normally causes the shell to echo exactly which
commands are being executed. Most shells will print
the substituted variables (eg. `echo
mytarget.redo.tmp`) and not the original source line
(eg. `echo $3`).
-k, --keep-going
: keep building as many targets as possible even if some
of them return an error. If one target fails, any
target that depends on it also cannot be built, of course.
--shuffle
: randomize the order in which requested targets are
built. Normally, if you run `redo a b c`, the targets
will be built exactly in that order: first `a`, then
`b`, then `c`. But if you use `-j`, they might end up
being built in parallel, so it isn't safe to rely on
this precise ordering. Using `--shuffle`, redo will
build its targets in random order even without `-j`,
which makes it easier to find accidental dependency
problems of this sort. NOTE: if you really just want
to guarantee that `a` is built, then `b`, then `c`, you
can just run three `redo` commands consecutively.
Because your .do script is just a script, it will not
be accidentally parallelized.
--no-details
: display *only* the messages from redo itself, not the other messages
produced by build scripts. Generally this gives you a list of which
targets were built, but not detailed logs, warnings, or errors.
--no-status
: don't display the running build status at the bottom of the screen.
(Unless this option is specified, the status line will be enabled
if using --follow, if stderr is a terminal.) If stderr is *not* a
terminal, you can force enable the status line using --status.
--no-pretty
: display "raw" redo log lines (@@REDO events) rather than using a
human-readable format. The default is --pretty.
--no-color
: when using --pretty and writing to a terminal, colorize the output to
make results stand out more clearly. If not writing to a terminal, you
can use --color to force colorized output.
--no-log
: don't capture stderr log messages from build scripts. This prevents
redo-log from redisplaying the logs later, and if using --jobs, causes
output from all parallel jobs to be jumbled together. This was the
only behaviour available before redo-0.30. The default is --log.
--debug-locks
: print messages about acquiring, releasing, and waiting
on locks. Because redo can be highly parallelized,
one instance may end up waiting for a target to be
built by some other instance before it can continue.
If you suspect this is causing troubles, use this
option to see which instance is waiting and when.
--debug-pids
: add the process id of the particular redo instance to each
output message. This makes it easier to figure out
which sub-instance of redo is doing what.
--version
: displays the redo version number.
# DISCUSSION
The core of redo is extremely simple. When you type `redo
targetname`, then it will search for a matching .do file
based on a simple algorithm. For example, given a target
named `mytarget.a.b.c.d`, redo will look for a .do file in
the following order:
- mytarget.a.b.c.d.do
- default.a.b.c.d.do
- default.b.c.d.do
- default.c.d.do
- default.d.do
- default.do
In all cases, the .do file must be in the same directory as
the target file, or in one of the target's parent
directories. For example, if given a target named
`../a/b/xtarget.y`, redo will look for a .do file in the
following order:
- $PWD/../a/b/xtarget.y.do
- $PWD/../a/b/default.y.do
- $PWD/../a/b/default.do
- $PWD/../a/default.y.do
- $PWD/../a/default.do
- $PWD/../default.y.do
- $PWD/../default.do
The first matching .do file is executed as a `/bin/sh`
script. The .do script is always executed with the current
working directory set to the directory containing the .do
file. Because of that rule, the
following two commands always have exactly identical
behaviour:
redo path/to/target
cd path/to && redo target
(Note: in `make`(1), these commands have confusingly
different semantics. The first command would look for a
target named `path/to/target` in `./Makefile`, while the
second command would look for a target named `target` in
`./path/to/Makefile`. The two Makefiles might give
completely different results, and it's likely that the
first command would have incomplete dependency information.
redo does not have this problem.)
The three arguments passed to the .do script are:
- $1: the target name (eg. mytarget.a.b)
- $2: the basename of the target, minus its extension (eg. mytarget)
- $3: a temporary filename that the .do script should write
its output to.
Instead of using $3, the .do script may also write the
produced data to stdout.
If the .do file is in the same directory as the target, $1
is guaranteed to be a simple filename (with no path
component). If the .do file is in a parent directory of
the target, $1 and $3 will be relative paths (ie. will
contain slashes).
redo is designed to update its targets atomically, and only
if the do script succeeds (ie. returns a zero exit code).
Thus, you should never write directly to the target file,
only to $3 or stdout.
Normally, a .do script will call other .do scripts
recursively, by running either `redo` (which will always
build the sub-target) or `redo-ifchange` (which only
rebuilds the sub-target if its dependencies have changed).
Running `redo-ifchange` is also the way your .do script
declares dependencies on other targets; any target that is
`redo-ifchange`d during your .do script's execution is both
executed (if needed) and added as a dependency.
You may have heard that 'recursive make is considered
harmful' (http://miller.emu.id.au/pmiller/books/rmch/).
Unlike `make`(1), redo does correct locking, state
management, and global dependency checking, so none of the
arguments in that essay apply to redo. In fact, recursive
redo is really the only kind of redo.
# RELATED COMMANDS
When writing a .do script, it will probably need to run
one or more of the following commands:
`redo [targets...]`
: to build a sub-target unconditionally.
`redo-ifchange [targets...]`
: to declare dependencies on the given files, and build them if
they don't yet exist or are outdated.
`redo-ifcreate [sources...]`
: to tell redo that the current target must be rebuilt if
the given source files (which must not yet exist) get created.
`redo-always`
: to tell redo that the current target must always be
rebuilt, even if none of its dependencies have changed.
(You might need this for targets that depend on more than just
file contents. For example, the output of `ls *.c`
changes when files are created or deleted, but there is no way
for redo to know that without re-running the command.)
`echo "stamp contents..." | redo-stamp`
: to tell redo that even though the current target has
been rebuilt, it may not actually be any different from
the previous version, so targets that depend on it
might not need to be rebuilt. Often used in
conjunction with `redo-always` to reduce the impact of
always rebuilding a target.
There are also some less common ones:
`redo-ood`
: Get a list of all known targets that have been built before, but
are currently out of date.
`redo-targets`
: Get a list of all known targets that have been built before.
`redo-sources`
: Get a list of all known redo source files that still exist.
`redo-whichdo <target>`
: Explain the search path used to find a .do file for the given
target.
# CREDITS
The original concept for `redo` was created by D. J.
Bernstein and documented on his web site
(http://cr.yp.to/redo.html). This independent implementation
was created by Avery Pennarun and you can find its source
code at http://github.com/apenwarr/redo.
# SEE ALSO
`sh`(1), `make`(1),
`redo-ifchange`(1), `redo-ifcreate`(1), `redo-always`(1),
`redo-stamp`(1), `redo-ood`(1), `redo-targets`(1), `redo-sources`(1),
`redo-whichdo`(1)