files: respect gitignore when uploading files

[VMois]

Now reana-client upload command will respect .gitignore files.

Expected behavior:

• upload all input.files, ignore .gitignore in this case;

• upload all files or directories from input.directories that are not matched by .gitignore;

• empty directories will not be uploaded

How to test:

1. Go to the reana-demo-atlas-recast example.

2. Create a .gitignore file there with the following content:

do-not-upload-*/
*.py[cod]

3. Go to the workflow/ directory. Create files that will be ignored:

echo "Hello" > some_python.pyc
mkdir do-not-upload-me
echo "World" > do-not-upload-me/text.txt

4. Run example (with run), you can see that files that match .gitignore are not uploaded.

5. Check if reana-client works as before when .gitignore doesn't exist.

addresses #406

[codecov-commenter]

Codecov Report

Merging #603 (041e17c) into master (cfd526e) will decrease coverage by 0.13%. The diff coverage is 27.27%.

@@            Coverage Diff             @@
##           master     #603      +/-   ##
==========================================
- Coverage   55.84%   55.71%   -0.14%     
==========================================
  Files          23       23              
  Lines        2258     2267       +9     
==========================================
+ Hits         1261     1263       +2     
- Misses        997     1004       +7     

Impacted Files	Coverage Δ
reana_client/cli/files.py	70.31% <27.27%> (-1.58%)	:arrow_down:

[VMois]

can you add a note in the changelog?

Done.

PS. We have version 0.8.2 as unreleased in the changelog. Not sure what to do with it.