Signed-off-by: Michael Brown <mcb30@ipxe.org>

Refactor the {load,exec} image operations as {probe,exec}.  This makes
the probe mechanism cleaner, eliminates some forward declarations,
avoids holding magic state in image->priv, eliminates the possibility
of screwing up between the "load" and "exec" stages, and makes the
documentation simpler since the concept of "loading" (as distinct from
"executing") no longer needs to be explained.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

The online documentation (e.g. http://ipxe.org/cmd/ifopen), though not
yet complete, is far more comprehensive than could be provided within
the iPXE binary.  Save around 200 bytes (compressed) by removing the
command descriptions from the interactive help, and instead referring
users directly to the web page describing the relevant command.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

The && and || operators should be left-associative, since that is how
they are treated in most other languages (including C and Unix
shell).  For example, in the command:

  dhcp net0 && goto dhcp_ok || echo No DHCP on net0

if the "dhcp net0" fails then the "echo" should be executed.

After an "exit" or a successful "goto", further commands on the same
line should never be executed.  For example:

  goto somewhere && echo This should never be printed
  exit 0 && echo This should never be printed
  exit 1 && echo This should never be printed

An "exit" should cause the current shell or script to terminate and
return the specified exit status to its caller.  For example:

  chain test.ipxe && echo Success || echo Failure
    [in test.ipxe]
    #!ipxe
    exit 0

should echo "Success".

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Allow script labels to be defined using the syntax

  :<labelname>

(nothing else allowed on the line, including whitespace).  Labels are
ignored during script execution, but can be used as the target of the
"goto" command.  For example:

  #!ipxe

  goto machine_${net0/ip} || goto machine_default

  # Linux kernel boot
  :machine_10.0.0.101
  :machine_10.0.0.102
  set filename http://my.boot.server/vmlinuz
  goto done

  # Default configuration
  :machine_default
  set filename pxelinux.0
  goto done

  # Boot selected configuration
  :done
  chain ${filename}

Originally-implemented-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>
Originally-implemented-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Access to the gpxe.org and etherboot.org domains and associated
resources has been revoked by the registrant of the domain.  Work
around this problem by renaming project from gPXE to iPXE, and
updating URLs to match.

Also update README, LOG and COPYRIGHTS to remove obsolete information.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Windows text editors such as Notepad tend to use CRLF line endings,
which breaks gPXE's signature detection for script images.  Since
scripts are usually very small, they end up falling back to being
detected as valid PXE executable images (since there are no signature
checks for PXE executables).  Executing text files as x86 machine code
tends not to work well.

Fix by allowing for any isspace() character to terminate the "#!gpxe"
signature, and by ensuring that CR characters get stripped during
command line parsing.

Suggested-by: Shao Miller <Shao.Miller@yrdsb.edu.on.ca>

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

Multi-level menus via COMBOOT rely on the COMBOOT program being able
to exit and invoke a new COMBOOT program (the next menu).  This works,
but rapidly (within about five iterations) runs out of space in gPXE's
internal stack, since each new image is executed in a new function
context.

Fix by allowing tail recursion between images; an image can now
specify a replacement image for itself, and image_exec() will perform
the necessary tail recursion.

Both the script and PXE images types will claim a zero-length image.
Inhibit this to avoid end-user surprises.

executing any image, not just a script.  (This will enable pxelinux to
use relative URIs, should it wish to.)

Print error status using strerror().

allows us to avoid execution loops without having to hack around the
image registration order.

Add scripts as an image format (since it's trivial to do).