Commit only when necessary

[CasperWA]

The update_docs.sh script used to update the changelog and more upon a new release is set to exit at any time if a return value different than 0 occurs (set -e).

Since git will return a non-zero value if trying to commit and there's nothing to commit, a check for this has been added to update_docs.sh.

It is not done for the second git commit line, since if there is no CHANGELOG to commit, I would suspect there shouldn't be a release at all. However, this can be argued against.

[codecov]

Codecov Report

Merging #495 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #495   +/-   ##
=======================================
  Coverage   91.58%   91.58%           
=======================================
  Files          61       61           
  Lines        3103     3103           
=======================================
  Hits         2842     2842           
  Misses        261      261           

Flag	Coverage Δ
#project	91.58% <ø> (ø)
#validator	63.61% <ø> (ø)

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