Add a bunch of manpages.

Documentation/redo-ifchange.md

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+% redo-ifchange(1) Redo 0.00
+% Avery Pennarun <apenwarr@gmail.com>
+% 2010-12-12
+
+# NAME
+
+redo-ifchange - rebuild target files when source files have changed
+
+# SYNOPSIS
+
+redo-ifchange [targets...]
+
+
+# DESCRIPTION
+
+Normally redo-ifchange is run from a .do file that has been
+executed by `redo`(1).  See `redo`(1) for more details.
+
+redo-ifchange doesn't take any command line options other
+than a list of *targets*.  To provide command line options,
+you need to run `redo` instead.
+
+redo-ifchange performs the following steps:
+
+- it creates a dependency on the given *targets*.  If any
+  of those targets change in the future, the current target
+  (the one calling redo-ifchange) will marked as needing to
+  be rebuilt.
+  
+- for any *target* that is out of date, it calls the
+  equivalent of `redo target`.
+
+- for any *target* that is locked (because some other
+  instance of `redo` or `redo-ifchange` is already building
+  it), it waits until the lock is released.
+  
+redo-ifchange returns only after all the given
+*targets* are known to be up to date.
+
+
+# TIP
+
+You don't have to run redo-ifchange *before* generating
+your target; you can generate your target first, then
+declare its dependencies.  For example, as part of
+compiling a .c file, gcc learns the list
+of .h files it depends on. You can pass this information
+along to redo-ifchange, so if any of those headers are
+changed or deleted, your .c file will be rebuilt:
+
+        redo-ifchange $1$2
+        gcc -o $3 -c $1$2 \
+            -MMD -MF $1.deps -MT DELETE_ME
+        redo-ifchange $(sed -e 's,^DELETE_ME:,,' \
+                            -e 's,\\,,' $1.deps)
+
+This is much less confusing than the equivalent
+autodependency mechanism in `make`(1), because make
+requires that you declare all your dependencies before
+running the target build commands.
+
+
+# REDO
+
+Part of the `redo`(1) suite.
+    
+# 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
+
+`redo`(1), `redo-ifcreate`(1), `redo-always`(1), `redo-stamp`(1)