Add help target to the makefile

[philderbeast]

Fix #10596. Add help for some of the makefile targets.

$ make help
all                            Build the Cabal libraries and cabal-install executables.
checks                         Run all local checks; whitespace, style, and lint.
doctest-install                Install doctest tool needed for running doctests.
doctest                        Run doctests.
exe                            Builds the cabal-install executables.
fix-whitespace                 Run fix-whitespace in fix mode.
ghcid-cli                      Run ghcid for the cabal-install executable.
ghcid-lib                      Run ghcid for the Cabal library.
help-banner                    Show the help banner.
help                           Show the commented targets.
init                           Set up git hooks and ignored revisions.
lib                            Builds the Cabal libraries.
lint-json                      Run HLint in JSON mode.
lint                           Run HLint.
style-commit                   Run the code styler on the previous commit.
style-modified                 Run the code styler on modified files.
style                          Run the code styler.
tags                           Generate editor tags, vim ctags and emacs etags.
users-guide                    Build the users guide.
users-guide-requirements       Install the requirements for building the users guide.
whitespace                     Run fix-whitespace in check mode.

---

Template B: This PR does not modify behaviour or interface

E.g. the PR only touches documentation or tests, does refactorings, etc.

Include the following checklist in your PR:

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[philderbeast]

Label merge+no rebase is necessary when the pull request is from an organisation.

[philderbeast]

The help after #10603 was merged to master.

Tip

Should we switch from prefix/infix to suffix for fix, from -fix-* to *-fix, for the fixing targets?

@geekosaur, you chose the prefix name for fix-whitespace in 2858dc0 and that matches the tool name. On the other hand the lexical grouping works better with a suffix.

$ make help
  all                            Build the Cabal libraries and cabal-install executables.
  checks                         Run all local checks; whitespace, typos, style, and lint.
  doctest-install                Install doctest tool needed for running doctests.
  doctest                        Run doctests.
  exe                            Builds the cabal-install executables.
- fix-whitespace                 Run fix-whitespace in fix mode.
  ghcid-cli                      Run ghcid for the cabal-install executable.
  ghcid-lib                      Run ghcid for the Cabal library.
  help-banner                    Show the help banner.
  help                           Show the commented targets.
  init                           Set up git hooks and ignored revisions.
  lib                            Builds the Cabal libraries.
  lint-json                      Run HLint in JSON mode.
  lint                           Run HLint.
- markdown-fix-typos             Fix typos in markdown files
  markdown-typos                 Find typos in markdown files
+ markdown-typos-fix             Fix typos in markdown files
  style-commit                   Run the code styler on the previous commit.
  style-modified                 Run the code styler on modified files.
  style                          Run the code styler.
  tags                           Generate editor tags, vim ctags and emacs etags.
  typos-install                  Install typos-cli for typos target using cargo
  users-guide                    Build the users guide.
- users-guide-fix-typos          Fix typos in users guide
  users-guide-requirements       Install the requirements for building the users guide.
  users-guide-typos              Find typos in users guide
+ users-guide-typos-fix          Fix typos in users guide
  whitespace                     Run fix-whitespace in check mode.
+ whitespace-fix                 Run fix-whitespace in fix mode.  

[geekosaur]

There's also DevX vs. what makes the help text look better.

[philderbeast]

One thing I hadn't noted earlier is the number of groups with a common prefix that we have already:

• doctest → doctest + doctest-install
• ghcid → ghcid-cli + ghcid-lib
• lint → lint + lint-json
• style → style + style-commit + style-modified
• users-guide → users-guide + users-guide-requirements

We have could have common suffixes too; -install, -check and -fix.