Adds get_predecessors() to grapht

[johnfxgalea]

grapht already has get_successors(). This PR adds get_predecessors().

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[johnfxgalea]

@martin-cs PTAL

[martin-cs]

Looks good.

[tautschnig]

Looks good to me, but it would be nice to have a test or some other actual use in the code base. Otherwise, the code might not ever get compiled and may silently stop working (for it's templated).

[codecov]

Codecov Report

Merging #6158 (12ace9e) into develop (cf594b8) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 12ace9e differs from pull request most recent head a3c1e1e. Consider uploading reports for the commit a3c1e1e to get more accurate results

@@             Coverage Diff             @@
##           develop    #6158      +/-   ##
===========================================
+ Coverage    74.91%   74.92%   +0.01%     
===========================================
  Files         1450     1450              
  Lines       158253   158265      +12     
===========================================
+ Hits        118550   118575      +25     
+ Misses       39703    39690      -13     

Impacted Files	Coverage Δ
src/util/graph.h	97.28% <ø> (ø)
unit/util/graph.cpp	100.00% <100.00%> (ø)
src/ansi-c/c_typecheck_base.cpp	50.54% <0.00%> (-27.75%)	⬇️
src/util/cmdline.cpp	69.94% <0.00%> (-25.44%)	⬇️
src/goto-programs/remove_returns.cpp	75.31% <0.00%> (-24.06%)	⬇️
src/ansi-c/literals/convert_character_literal.cpp	53.84% <0.00%> (-17.95%)	⬇️
src/ansi-c/c_typecheck_typecast.cpp	55.00% <0.00%> (-15.00%)	⬇️
src/util/xml.cpp	62.83% <0.00%> (-10.14%)	⬇️
src/ansi-c/ansi_c_convert_type.cpp	72.61% <0.00%> (-6.12%)	⬇️
src/ansi-c/type2name.cpp	84.91% <0.00%> (-5.03%)	⬇️
... and 17 more

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[johnfxgalea]

Done. PTAL

[tautschnig]

Done. PTAL

Thank you for adding the test! Can I be a pain and ask for the formatting commit to be squashed into the commit introducing the test? Well, and perhaps also craft a slightly more unambiguous commit message for that one?

[johnfxgalea]

Done. PTAL

Thank you for adding the test! Can I be a pain and ask for the formatting commit to be squashed into the commit introducing the test? Well, and perhaps also craft a slightly more unambiguous commit message for that one?

Sorry, I thought you were going to squash and merge via the Github button.

Done.