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

["Avi Halachmi (:avih) via GitGitGadget" <gitgitgadget@gmail.com>]

From: "Avi Halachmi (:avih)" <avihpit@yahoo.com>

$'...' is new in POSIX (2024), and some shells support it in recent
versions, while others have had it for decades (bash, zsh, ksh93).

However, there are still enough shells which don't support it, and
it's cheap to provide a fallback for them, so let's do that instead
of dismissing it as "it's compliant".

shells where $'...' works:
- bash, zsh, ksh93, mksh, busybox-ash, dash master, free/net bsd sh.

shells where it doesn't work, but the new fallback works:
- all dash releases (up to 0.5.12), older versions of free/net bsd sh,
  openbsd sh, pdksh, all Schily Bourne sh variants, yash.

Signed-off-by: Avi Halachmi (:avih) <avihpit@yahoo.com>
---
 contrib/completion/git-prompt.sh | 52 +++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 5d7f236fe48..bbc16417ac9 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -111,6 +111,17 @@
 __git_printf_supports_v=
 printf -v __git_printf_supports_v -- '%s' yes >/dev/null 2>&1
 
+__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
+
 # stores the divergence from upstream in $p
 # used by GIT_PS1_SHOWUPSTREAM
 __git_ps1_show_upstream ()
@@ -118,7 +129,7 @@ __git_ps1_show_upstream ()
 	local key value
 	local svn_remotes="" svn_url_pattern="" count n
 	local upstream_type=git legacy="" verbose="" name=""
-	local LF=$'\n'
+	local LF="$__git_LF"
 
 	# get some config options from git-config
 	local output="$(git config -z --get-regexp '^(svn-remote\..*\.url|bash\.showupstream)$' 2>/dev/null | tr '\0\n' '\n ')"
@@ -271,12 +282,16 @@ __git_ps1_colorize_gitstring ()
 		local c_lblue='%F{blue}'
 		local c_clear='%f'
 	else
-		# Using \001 and \002 around colors is necessary to prevent
-		# issues with command line editing/browsing/completion!
-		local c_red=$'\001\e[31m\002'
-		local c_green=$'\001\e[32m\002'
-		local c_lblue=$'\001\e[1;34m\002'
-		local c_clear=$'\001\e[0m\002'
+		# \001 (SOH) and \002 (STX) are 0-width substring markers
+		# which bash/readline identify while calculating the prompt
+		# on-screen width - to exclude 0-screen-width esc sequences.
+		local c_pre="${__git_SOH}${__git_ESC}["
+		local c_post="m${__git_STX}"
+
+		local c_red="${c_pre}31${c_post}"
+		local c_green="${c_pre}32${c_post}"
+		local c_lblue="${c_pre}1;34${c_post}"
+		local c_clear="${c_pre}0${c_post}"
 	fi
 	local bad_color="$c_red"
 	local ok_color="$c_green"
@@ -312,7 +327,7 @@ __git_ps1_colorize_gitstring ()
 # variable, in that order.
 __git_eread ()
 {
-	test -r "$1" && IFS=$'\r\n' read -r "$2" <"$1"
+	test -r "$1" && IFS=$__git_CRLF read -r "$2" <"$1"
 }
 
 # see if a cherry-pick or revert is in progress, if the user has committed a
@@ -430,19 +445,20 @@ __git_ps1 ()
 		return "$exit"
 	fi
 
+	local LF="$__git_LF"
 	local short_sha=""
 	if [ "$rev_parse_exit_code" = "0" ]; then
-		short_sha="${repo_info##*$'\n'}"
-		repo_info="${repo_info%$'\n'*}"
+		short_sha="${repo_info##*$LF}"
+		repo_info="${repo_info%$LF*}"
 	fi
-	local ref_format="${repo_info##*$'\n'}"
-	repo_info="${repo_info%$'\n'*}"
-	local inside_worktree="${repo_info##*$'\n'}"
-	repo_info="${repo_info%$'\n'*}"
-	local bare_repo="${repo_info##*$'\n'}"
-	repo_info="${repo_info%$'\n'*}"
-	local inside_gitdir="${repo_info##*$'\n'}"
-	local g="${repo_info%$'\n'*}"
+	local ref_format="${repo_info##*$LF}"
+	repo_info="${repo_info%$LF*}"
+	local inside_worktree="${repo_info##*$LF}"
+	repo_info="${repo_info%$LF*}"
+	local bare_repo="${repo_info##*$LF}"
+	repo_info="${repo_info%$LF*}"
+	local inside_gitdir="${repo_info##*$LF}"
+	local g="${repo_info%$LF*}"
 
 	if [ "true" = "$inside_worktree" ] &&
 	   [ -n "${GIT_PS1_HIDE_IF_PWD_IGNORED-}" ] &&
-- 
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