regenerate git-svn .rev_map file

git-svn-revmap.awk

#! /usr/bin/env gawk -f
# git --no-pager log | gawk -f this-script > revmap.txt
# xxd -c 24 -r revmap.txt \
#    .git/svn/refs/remotes/trunk/.rev_map.cfe28804-0f27-0410-a406-dd0f0b0b656f
# 0000000: 0000 0001 cce6 285e 48e1 e3cc 0d7d 0617 beb0 4e88 a126 8634  
# 0000018: 0000 0006 6e4f ada4 bed4 6660 c987 dc74 1243 8973 16cc c810  
BEGIN {
    FS=" "
    # this number comes from ``git --no-pager log | grep ^commit | wc -l``
    # and is ZERO-indexed because the last xxd will begin with 0000
    # you might be tempted to think it is the highest r-number, but no,
    # because evidently not every subversion commit made it to git
    cnt=30554
}
/^commit / {
    cmit=$2
}
/git-svn/ {
    # remove everything except the r-number
    sub(/[^@]+@/,"")
    # remove the repository-id
    sub(/ .*$/,"")
    addr=cnt * 24
    # thankfully, xxd is tolerant of not having
    # any spaces, so we can just dump the commitish
    # right into the file
    printf "%08x: %08x%s  \n", addr, $0, cmit
    cnt = cnt - 1
}