config/git: import suckless sbase

i currently use the output of sha512sum in several
places of xbmk, which is a bit unreliable in case
output changes.

other cases where i use util outputs in variables
are probably reliable, because i'm using mostly
posix utilities in those.

to mitigate this, i now import suckless sbase, which
has a reasonable sha512sum implementation.

*every* binary it builds is being placed in build.list,
because i'll probably start using more of them.

for example, i may start modifying the "date"
implementation, adding the GNU-specific options that
i need as mentioned on init.sh

i'm importing it in util/ because the sha512sum
util is needed for verifying project sources, so
if sbase itself is a "project source", that means
we can into a chicken and egg bootstrapping problem.

this is sbase at revision:
055cc1ae1b3a13c3d8f25af0a4a3316590efcd48

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/sbase/expr.1

@@ -0,0 +1,101 @@
+.Dd October 8, 2015
+.Dt EXPR 1
+.Os sbase
+.Sh NAME
+.Nm expr
+.Nd evaluate expression
+.Sh SYNOPSIS
+.Nm
+.Ar expression
+.Sh DESCRIPTION
+.Nm
+evaluates
+.Ar expression
+and writes the result to stdout.
+.Pp
+There are two elemental expressions,
+.Sy integer
+and
+.Sy string .
+Let
+.Sy expr
+be a non-elemental expression and
+.Sy expr1 ,
+.Sy expr2
+arbitrary expressions.
+Then
+.Sy expr
+has the recursive form
+.Sy expr = [(] expr1 operand expr2 [)] .
+.Pp
+With
+.Sy operand
+being in order of increasing precedence:
+.Bl -tag -width Ds
+.It |
+Evaluate to
+.Sy expr1
+if it is neither an empty string nor 0; otherwise evaluate to
+.Sy expr2 .
+.It &
+Evaluate to
+.Sy expr1
+if
+.Sy expr1
+and
+.Sy expr2
+are neither empty strings nor 0; otherwise evaluate to 0.
+.It = > >= < <= !=
+If
+.Sy expr1
+and
+.Sy expr2
+are integers, evaluate to 1 if the relation is true and 0 if it is false.
+If
+.Sy expr1
+and
+.Sy expr2
+are strings, apply the relation to the return value of
+.Xr strcmp 3 .
+.It + -
+If
+.Sy expr1
+and
+.Sy expr2
+are integers, evaluate to their sum or subtraction.
+.It * / %
+If
+.Sy expr1
+and
+.Sy expr2
+are integers, evaluate to their multiplication, division or remainder.
+.It :
+Evaluate to the number of characters matched in
+.Sy expr1
+against
+.Sy expr2 . expr2
+is anchored with an implicit '^'.
+.Pp
+You can't directly match the empty string, since zero matched characters
+resolve equally to a failed match.
+To work around this limitation, use "expr X'' : 'X$' instead of "expr ''
+: '$'"
+.El
+.Sh EXIT STATUS
+.Bl -tag -width Ds
+.It 0
+.Ar expression
+is neither an empty string nor 0.
+.It 1
+.Ar expression
+is an empty string or 0.
+.It 2
+.Ar expression
+is invalid.
+.It > 2
+An error occurred.
+.El
+.Sh SEE ALSO
+.Xr test 1
+.Sh STANDARDS
+POSIX.1-2013.