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Re: [PATCH 2/7] help -a: do not list commands that are excluded from the build




"Johannes Schindelin via GitGitGadget" <gitgitgadget@xxxxxxxxx>
writes:

> From: Johannes Schindelin <johannes.schindelin@xxxxxx>
>
> When built with NO_CURL or with NO_UNIX_SOCKETS, some commands are
> skipped from the build. It does not make sense to list them in the
> output of `git help -a`, so let's just not.

The objective makes sense quite a lot.

>  command-list.h: $(wildcard Documentation/git*.txt) Documentation/*config.txt Documentation/config/*.txt
> -	$(QUIET_GEN)$(SHELL_PATH) ./generate-cmdlist.sh command-list.txt >$@+ && mv $@+ $@
> +	$(QUIET_GEN)$(SHELL_PATH) ./generate-cmdlist.sh \
> +		$(patsubst %,--exclude-program %,$(EXCLUDED_PROGRAMS)) \

Each whitespace separated token on $(EXCLUDED_PROGRAMS) is the name
of a program to be excluded and we know there is no funny characters
in it, hence quoing in "^$1 " (without protecting us against
funnies) is sufficient.

> +		command-list.txt >$@+ && mv $@+ $@
>  
>  SCRIPT_DEFINES = $(SHELL_PATH_SQ):$(DIFF_SQ):$(GIT_VERSION):\
>  	$(localedir_SQ):$(NO_CURL):$(USE_GETTEXT_SCHEME):$(SANE_TOOL_PATH_SQ):\
> diff --git a/generate-cmdlist.sh b/generate-cmdlist.sh
> index 709d67405b..7867b99d19 100755
> --- a/generate-cmdlist.sh
> +++ b/generate-cmdlist.sh
> @@ -6,7 +6,7 @@ die () {
>  }
>  
>  command_list () {
> -	grep -v '^#' "$1"
> +	eval grep -ve '^#' $exclude_programs "$1"

The original protects against $IFS in the filename given as $1, but
with the eval that is no longer true.  We have been feeding the
constant "command-list.txt" to the program since its inception, and
I do not expect it to change, so this regression in defensiveness
does not matter in practice.  Also because # is prefixed with ^, the
unintended loss of quotes around it when the eval makes the shell
re-parse the generated command line would not make the remainder
into a comment.

But it does look brittle, and smells like a trap for less
experienced shell programmers to blindly copy & paste & tweak
without understanding what is going on, leading to bugs.

	eval "grep -v -e '^#' $exclude_programs" <"$1"

or something like that, perhaps?

> @@ -93,6 +93,14 @@ EOF
>  EOF
>  }
>  
> +exclude_programs=
> +while test "a$1" = "a--exclude-program"

s/a/z/g; if you want to pretend to be old-fashioned, but s/a//g;
should be sufficient in the modern world.

> +do
> +	shift
> +	exclude_programs="$exclude_programs -e \"^$1 \""
> +	shift
> +done

As I said, this part looks good enough given the things we feed as
parameters to --exclude-program option.

Thanks.