ash: [VAR] Fix loss of variables when hash collides

ash: [VAR] Fix loss of variables when hash collides

Upstream commit:

    Date: Tue, 6 Jul 2010 17:40:53 +0800
    [VAR] Fix loss of variables when hash collides

    Brian Koropoff reported that the new var patches broke the following
    script:

    #!/bin/dash
    GDM_LANG="bar"
    OPTION="foo"
    unset GDM_LANG
    # OPTION has mysteriously become unset
    echo "$OPTION"

    He correctly diagnosed this as a result of removing all variables
    in the hash chain preceding the one that should be removed in
    setvareq.

    He also provided a patch to fix this.

    This patch is based on his but without keeping the original vpp.
    As a result, we now store new variables at the end of the hash
    chain instead of the beginning.

    To make this work, setvareq/setvar now returns the vp pointer
    modified.  In case they're used to unset a variable the pointer
    returned is undefined.  This is because mklocal needs it and
    used to get it by assuming that the new variable always appear
    at the beginning of the chain.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>