[PATCH v4 8/8] git-prompt: support custom 0-width PS1 markers

Avi Halachmi (:avih) via GitGitGadget
2024-08-20T01:48:43Z

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

When using colors, the shell needs to identify 0-width substrings
in PS1 - such as color escape sequences - when calculating the
on-screen width of the prompt.

Until now, we used the form %F{<color>} in zsh - which it knows is
0-width, or otherwise use standard SGR esc sequences wrapped between
byte values 1 and 2 (SOH, STX) as 0-width start/end markers, which
bash/readline identify as such.

But now that more shells are supported, the standard SGR sequences
typically work, but the SOH/STX markers might not be identified.

This commit adds support for vars GIT_PS1_COLOR_{PRE,POST} which
set custom 0-width markers or disable the markers.

Signed-off-by: Avi Halachmi (:avih) <avihpit@yahoo.com>
---
contrib/completion/git-prompt.sh | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 6be2f1dd901..6186c474ba7 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -129,11 +129,16 @@
# strings (SGR color sequences) when calculating the on-screen
# prompt width, to maintain correct input editing at the prompt.
#
-# Currently there's no support for different markers, so if editing
-# behaves weird when using colors in __git_ps1, then the solution
-# is either to disable colors, or, in some shells which only care
-# about the width of the last prompt line (e.g. busybox-ash),
-# ensure the git output is not at the last line, maybe like so:
+# To replace or disable the 0-width markers, set GIT_PS1_COLOR_PRE
+# and GIT_PS1_COLOR_POST to other markers, or empty (nul) to not
+# use markers. For instance, some shells support '\[' and '\]' as
+# start/end markers in PS1 - when invoking __git_ps1 with 3/4 args,
+# but it may or may not work in command substitution mode. YMMV.
+#
+# If the shell doesn't support 0-width markers and editing behaves
+# incorrectly when using colors in __git_ps1, then, other than
+# disabling color, it might be solved using multi-line prompt,
+# where the git status is not at the last line, e.g.:
# PS1='\n\w \u@\h$(__git_ps1 " (%s)")\n\$ '

# check whether printf supports -v
@@ -309,8 +314,8 @@ __git_ps1_colorize_gitstring ()
# \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${__git_STX}"
+ local c_pre="${GIT_PS1_COLOR_PRE-$__git_SOH}${__git_ESC}["
+ local c_post="m${GIT_PS1_COLOR_POST-$__git_STX}"

local c_red="${c_pre}31${c_post}"
local c_green="${c_pre}32${c_post}"
--
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