[PATCH] contrib/git-prompt.sh: handle missing 'printf -v' more gracefully

[Brandon Casey <bcasey@nvidia.com>]

From: Brandon Casey <drafnel@gmail.com>

Old Bash (3.0) which is distributed with RHEL 4.X and other ancient
platforms that are still in wide use, do not have a printf that
supports -v.  Neither does Zsh (which is already handled in the code).

As suggested by Junio, let's test whether printf supports the -v
option and store the result.  Then later, we can use it to
determine whether 'printf -v' can be used, or whether printf
must be called in a subshell.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
---

This replaces [PATCH 3/3] Revert "bash prompt: avoid command substitution
when finalizing gitstring".

This may or may not need to be updated to use "${var-}" depending on
your response to my other email, but this seems sufficient.

-Brandon

 contrib/completion/git-prompt.sh | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index a81ef5a..639888a 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -84,6 +84,10 @@
 # the colored output of "git status -sb" and are available only when
 # using __git_ps1 for PROMPT_COMMAND or precmd.
 
+# check whether printf supports -v
+__git_printf_supports_v=
+printf -v __git_printf_supports_v -- '%s' yes >/dev/null 2>&1
+
 # stores the divergence from upstream in $p
 # used by GIT_PS1_SHOWUPSTREAM
 __git_ps1_show_upstream ()
@@ -433,10 +437,10 @@ __git_ps1 ()
 	local gitstring="$c${b##refs/heads/}${f:+$z$f}$r$p"
 
 	if [ $pcmode = yes ]; then
-		if [[ -n ${ZSH_VERSION-} ]]; then
-			gitstring=$(printf -- "$printf_format" "$gitstring")
-		else
+		if test "$__git_printf_supports_v" = yes; then
 			printf -v gitstring -- "$printf_format" "$gitstring"
+		else
+			gitstring=$(printf -- "$printf_format" "$gitstring")
 		fi
 		PS1="$ps1pc_start$gitstring$ps1pc_end"
 	else
-- 
1.8.4.rc0.2.g6cf5c31


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