Subject: Re: [PATCH v2 02/11] GIT-VERSION-GEN: allow running without input and output files

From: Toon Claes <[email-masked]>
Date: Tue, 21 Jan 2025 14:16:11 +0100

Patrick Steinhardt <[email-masked]> writes:

> The GIT-VERSION-GEN script requires an input file containing formatting
> directives to be replaced as well as an output file that will get
> overwritten in case the file contents have changed. When computing the
> project version for Meson we don't want to have either though:
>
>   - We only want to compute the version without anything else, but don't
>     have an input file that would match that exact format. While we
>     could of course introduce a new file just for that usecase, it feels
>     suboptimal to add another file every time we want to have a slightly
>     different format for versioned data.
>
>   - The computed version needs to be read from stdout so that Meson can
>     wire it up for the project.
>
> Extend the script to handle both usecases by recognizing `--format=` as
> alternative to providing an input path and by writing to stdout in case
> no output file was given.
>
> Signed-off-by: Patrick Steinhardt <[email-masked]>
> ---
>  GIT-VERSION-GEN | 44 +++++++++++++++++++++++++++++---------------
>  1 file changed, 29 insertions(+), 15 deletions(-)
>
> diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
> index b8b683b9337e5771e14a2cfb84022a11489bb432..9d201a98fd2766911544225c62159cbfe8dff5fe 100755
> --- a/GIT-VERSION-GEN
> +++ b/GIT-VERSION-GEN
> @@ -5,21 +5,29 @@ DEF_VER=v2.48.0
>  LF='
>  '
>  
> -if test "$#" -ne 3
> +if test "$#" -lt 2 || test "$#" -gt 3
>  then
> -    echo >&2 "USAGE: $0 <SOURCE_DIR> <INPUT> <OUTPUT>"
> +    echo >&2 "USAGE: $0 <SOURCE_DIR> (--format=<STRING>|<INPUT>) [<OUTPUT>]"
>      exit 1
>  fi
>  
>  SOURCE_DIR="$1"
> -INPUT="$2"
> -OUTPUT="$3"
>  
> -if ! test -f "$INPUT"
> -then
> -	echo >&2 "Input is not a file: $INPUT"
> -	exit 1
> -fi
> +case "$2" in
> +--format=*)
> +	INPUT="${2#--format=}"
> +	;;
> +*)
> +	if ! test -f "$2"
> +	then
> +		echo >&2 "Input is not a file: $2"
> +		exit 1
> +	fi
> +	INPUT=$(cat "$2")
> +	;;
> +esac
> +
> +OUTPUT="$3"
>  
>  # Protect us from reading Git version information outside of the Git directory
>  # in case it is not a repository itself, but embedded in an unrelated
> @@ -74,19 +82,25 @@ read GIT_MAJOR_VERSION GIT_MINOR_VERSION GIT_MICRO_VERSION GIT_PATCH_LEVEL trail
>  $(echo "$GIT_VERSION" 0 0 0 0 | tr '.a-zA-Z-' ' ')
>  EOF
>  
> -sed -e "s|@GIT_VERSION@|$GIT_VERSION|" \
> +REPLACED=$(printf "%s" "$INPUT" | sed -e "s|@GIT_VERSION@|$GIT_VERSION|" \
>  	-e "s|@GIT_MAJOR_VERSION@|$GIT_MAJOR_VERSION|" \
>  	-e "s|@GIT_MINOR_VERSION@|$GIT_MINOR_VERSION|" \
>  	-e "s|@GIT_MICRO_VERSION@|$GIT_MICRO_VERSION|" \
>  	-e "s|@GIT_PATCH_LEVEL@|$GIT_PATCH_LEVEL|" \
>  	-e "s|@GIT_BUILT_FROM_COMMIT@|$GIT_BUILT_FROM_COMMIT|" \
>  	-e "s|@GIT_USER_AGENT@|$GIT_USER_AGENT|" \
> -	-e "s|@GIT_DATE@|$GIT_DATE|" \
> -	"$INPUT" >"$OUTPUT".$$+
> +	-e "s|@GIT_DATE@|$GIT_DATE|"
> +)
>  
> -if ! test -f "$OUTPUT" || ! cmp "$OUTPUT".$$+ "$OUTPUT" >/dev/null
> +if test -z "$OUTPUT"
>  then
> -	mv "$OUTPUT".$$+ "$OUTPUT"
> +	printf "%s\n" "$REPLACED"
>  else
> -	rm "$OUTPUT".$$+
> +	printf "%s\n" "$REPLACED" >"$OUTPUT".$$+
> +	if ! test -f "$OUTPUT" || ! cmp "$OUTPUT".$$+ "$OUTPUT" >/dev/null
> +	then
> +		mv "$OUTPUT".$$+ "$OUTPUT"
> +	else
> +		rm "$OUTPUT".$$+
> +	fi
>  fi
>
> -- 
> 2.48.0.257.gd3603152ad.dirty

I was considering to suggest to have GIT-VERSION-GEN accept --stdin for
$INPUT and have it read from stdin instead of passing the format as an
argument, but looking at the following commits I agree with your
approach.

--
Toon