$ buildg.sh debug --cache-reuse /tmp/ctx
INFO[2022-05-31T11:44:56Z] storing the build data to "/home/ktock/.local/share/buildg/data". to prune the data, remove that directory manually. 
WARN[2022-05-31T11:44:56Z] using host network as the default            
#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 108B done
#1 DONE 0.0s

#2 [internal] load .dockerignore
#2 transferring context: 2B done
#2 DONE 0.0s

#3 [internal] load metadata for docker.io/library/busybox:latest
INFO[2022-05-31T11:44:58Z] CACHED [1/4] FROM docker.io/library/busybox@sha256:ebadf81a7f2146e95f8c850ad7af8cf9755d31cdba380a8ffd5930fba5996095 
INFO[2022-05-31T11:44:58Z] debug session started. type "help" for command reference. 
Filename: "Dockerfile"
 =>   1| FROM busybox
      2| RUN echo foo > /foo
      3| RUN echo bar > /bar
      4| RUN echo fail > /
(buildg) n
#3 DONE 1.9s

#4 [1/4] FROM docker.io/library/busybox@sha256:ebadf81a7f2146e95f8c850ad7af8cf9755d31cdba380a8ffd5930fba5996095
#4 resolve docker.io/library/busybox@sha256:ebadf81a7f2146e95f8c850ad7af8cf9755d31cdba380a8ffd5930fba5996095 0.0s done
#4 DONE 0.0s
INFO[2022-05-31T11:45:02Z] CACHED [2/4] RUN echo foo > /foo             
Filename: "Dockerfile"
      1| FROM busybox
 =>   2| RUN echo foo > /foo
      3| RUN echo bar > /bar
      4| RUN echo fail > /
(buildg) exec cat /foo
foo
(buildg) b 3
(buildg) c
INFO[2022-05-31T11:45:08Z] CACHED [3/4] RUN echo bar > /bar             
Breakpoint[0]: reached line: Dockerfile:3
Filename: "Dockerfile"
      1| FROM busybox
      2| RUN echo foo > /foo
*=>   3| RUN echo bar > /bar
      4| RUN echo fail > /
(buildg) exec cat /foo /bar
foo
bar
(buildg) n

#5 [2/4] RUN echo foo > /foo
#5 CACHED

#6 [3/4] RUN echo bar > /bar
#6 CACHED

#7 [4/4] RUN echo fail > /
Breakpoint[on-fail]: caught error process "/bin/sh -c echo fail > /" did not complete successfully: exit code: 1
Filename: "Dockerfile"
      1| FROM busybox
      2| RUN echo foo > /foo
*     3| RUN echo bar > /bar
 =>   4| RUN echo fail > /
(buildg) q
#7 0.065 /bin/sh: can't create /: Is a directory
#7 CANCELED