completion: clear cached --options when sourcing the completion script

The established way to update the completion script in an already
running shell is to simply source it again: this brings in any new
--options and features, and clears caching variables.  E.g. it clears
the variables caching the list of (all|porcelain) git commands, so
when they are later lazy-initialized again, then they will list and
cache any newly installed commmands as well.

Unfortunately, since d401f3d (git-completion.bash: introduce
__gitcomp_builtin, 2018-02-09) and subsequent patches this doesn't
work for a lot of git commands' options.  To eliminate a lot of
hard-to-maintain hard-coded lists of options, those commits changed
the completion script to use a bunch of programmatically created and
lazy-initialized variables to cache the options of those builtin
porcelain commands that use parse-options.  These variables are not
cleared upon sourcing the completion script, therefore they continue
caching the old lists of options, even when some commands recently
learned new options or when deprecated options were removed.

Always 'unset' these variables caching the options of builtin commands
when sourcing the completion script.

Redirect 'unset's stderr to /dev/null, because ZSH's 'unset' complains
if it's invoked without any arguments, i.e. no variables caching
builtin's options are set.  This can happen, if someone were to source
the completion script twice without completing any --options in
between.  Bash stays silent in this case.

Add tests to ensure that these variables are indeed cleared when the
completion script is sourced; not just the variables caching options,
but all other caching variables, i.e. the variables caching commands,
porcelain commands and merge strategies as well.

Signed-off-by: SZEDER Gábor <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: szeder

contrib/completion/git-completion.bash

@@ -280,6 +280,10 @@ __gitcomp ()
 	esac
 }
 
+# Clear the variables caching builtins' options when (re-)sourcing
+# the completion script.
+unset $(set |sed -ne 's/^\(__gitcomp_builtin_[a-zA-Z0-9_][a-zA-Z0-9_]*\)=.*/\1/p') 2>/dev/null
+
 # This function is equivalent to
 #
 #    __gitcomp "$(git xxx --git-completion-helper) ..."

t/t9902-completion.sh

@@ -1497,4 +1497,35 @@ do
 	'
 done
 
+test_expect_success 'sourcing the completion script clears cached commands' '
+	__git_compute_all_commands &&
+	verbose test -n "$__git_all_commands" &&
+	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
+	verbose test -z "$__git_all_commands"
+'
+
+test_expect_success 'sourcing the completion script clears cached porcelain commands' '
+	__git_compute_porcelain_commands &&
+	verbose test -n "$__git_porcelain_commands" &&
+	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
+	verbose test -z "$__git_porcelain_commands"
+'
+
+test_expect_success 'sourcing the completion script clears cached merge strategies' '
+	__git_compute_merge_strategies &&
+	verbose test -n "$__git_merge_strategies" &&
+	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
+	verbose test -z "$__git_merge_strategies"
+'
+
+test_expect_success 'sourcing the completion script clears cached --options' '
+	__gitcomp_builtin checkout &&
+	verbose test -n "$__gitcomp_builtin_checkout" &&
+	__gitcomp_builtin notes_edit &&
+	verbose test -n "$__gitcomp_builtin_notes_edit" &&
+	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
+	verbose test -z "$__gitcomp_builtin_checkout" &&
+	verbose test -z "$__gitcomp_builtin_notes_edit"
+'
+
 test_done