`stg export` errors out when exporting a series that contains an empty patch

[agotsis]

rep.sh

#!/bin/bash

set -ex
# cleanup
rm -rf test export

mkdir test export && cd test

echo "hello" > file.txt

git init && git add file.txt && git commit -m "Initial commit"

stg init

# create a non-empty patch
echo "world" >> file.txt
stg new p1 -m p1 && stg refresh

# create an empty patch
stg new p2 -m p2

# try to export the series
stg export -n -d ../export

## ERROR: ##
# error: unrecognized input
# stg export: git failed with code 128
# <choked on empty patch it seems>

## EXPECTED: ##
# <empty, patches exported>

$ ./rep.sh
+ rm -rf test export
+ mkdir test export
+ cd test
+ echo hello
+ git init
Initialized empty Git repository in /home/agotsis/test/.git/
+ git add file.txt
+ git commit -m 'Initial commit'
[master (root-commit) f1a0559] Initial commit
 1 file changed, 1 insertion(+)
 create mode 100644 file.txt
+ stg init
+ echo world
+ stg new p1 -m p1
Now at patch "p1"
+ stg refresh
Now at patch "p1"
+ stg new p2 -m p2
Now at patch "p2"
+ stg export -n -d ../export
error: unrecognized input
stg export: git failed with code 128

$ ls export
01-p1  series

$ cat export/series
# This series applies on GIT commit f1a055946ffd00b5ed04d3e76106e3544f6d718a
01-p1
02-p2

$ stg -v
Stacked GIT 1.1
git version 2.28.0
Python version 3.8.5 (default, May 27 2021, 13:30:53)
[GCC 9.3.0]

$ git --version
git version 2.28.0

It would also appear that an empty patch in the middle has the same issues.

[jpgrayson]

@agotsis thank you for this issue report. Turns out stg import also had an issue with importing empty patches, which is now also resolved.

[agotsis]

Thanks for the quick fix!