Subject: Re: [PATCH 6/8] git-prompt: add fallback for shells without $'...'

From: Junio C Hamano <[email-masked]>
Date: Tue, 23 Jul 2024 13:25:22 -0700

"Avi Halachmi (:avih) via GitGitGadget" <[email-masked]>
writes:

> From: "Avi Halachmi (:avih)" <[email-masked]>
>
> $'...' is new in POSIX (2024), and some shells support it in recent
> versions, while others have had it for decades (bash, zsh, ksh93).

I will not look at this series futher during the current development
cycle that is about to conclude, but ...

> +__git_SOH=$'\1' __git_STX=$'\2' __git_ESC=$'\33'
> +__git_LF=$'\n' __git_CRLF=$'\r\n'
> +
> +if [ $'\101' != A ]; then  # fallback for shells without $'...'
> +   __git_CRLF=$(printf "\r\n\1\2\33")  # CR LF SOH STX ESC
> +   __git_ESC=${__git_CRLF#????}; __git_CRLF=${__git_CRLF%?}
> +   __git_STX=${__git_CRLF#???};  __git_CRLF=${__git_CRLF%?}
> +   __git_SOH=${__git_CRLF#??};   __git_CRLF=${__git_CRLF%?}
> +   __git_LF=${__git_CRLF#?}
> +fi

... given that these are not used literally in-place but are always
referred to by their __git_BYTE names, if we are making this script
portable across shells to the same degree as other shell scripts
following our coding guidelines, I would prefer to see it done
without any "fallback".

$(printf '\r') would work with bash, zsh and ksh93, too, and one
time assignment to these variables is not going to be performance
critical.  Just forbid use of $'\octal' notation in the coding
guidelines document, and implement just one variant.

Perhaps we should spell more things out that you wrote in some of
your proposed log messages more explicitly.  I think these have been
rules we have followed (grep for them in *.sh files outside
contrib/) but I did not find mention in the guidelines document.

Thanks.

 Documentation/CodingGuidelines | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git c/Documentation/CodingGuidelines w/Documentation/CodingGuidelines
index 1d92b2da03..bb058fcc87 100644
--- c/Documentation/CodingGuidelines
+++ w/Documentation/CodingGuidelines
@@ -107,6 +107,8 @@ For shell scripts specifically (not exhaustive):
 
  - We do not use Process Substitution <(list) or >(list).
 
+ - We do not use Dollar-Single-Quotes $'<octal>' notation.
+
  - Do not write control structures on a single line with semicolon.
    "then" should be on the next line for if statements, and "do"
    should be on the next line for "while" and "for".
@@ -140,7 +142,8 @@ For shell scripts specifically (not exhaustive):
 	sort >actual &&
 	...
 
- - We prefer "test" over "[ ... ]".
+ - We prefer "test" over "[ ... ]".  Never use "[[ ... ]]" unless in a
+   script only meant for bash.
 
  - We do not write the noiseword "function" in front of shell
    functions.