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[PATCH 15/19] bash prompt: use bash builtins to get detached HEAD abbrev. object name

From
SZEDER Gábor <szeder@ira.uka.de>
Date
May 9, 2012, 00:44 UTC
Message-ID
<1336524290-30023-16-git-send-email-szeder@ira.uka.de>
In-Reply-To
<1336524290-30023-1-git-send-email-szeder@ira.uka.de>

When describing a detached HEAD according to the $GIT_PS1_DESCRIBE environment variable fails, __git_ps1() runs the '$(cut -c1-7 .git/HEAD)' command substitution to put the 7 hexdigits abbreviated commit object name in the prompt. This imposes the overhead of fork()ing a subshell and fork(+exec()ing 'cut'.

Thanks to an earlier commit in this series the contents of HEAD is already read into a local variable, so we can get the 7 hexdigits using only parameter expansions, sparing the fork()+exec() overhead.

Since zsh doesn't implement substring expansion we can't just use ${head:0:7}, hence the "remove everything except the first 7 chars" parameter expansion combination.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
---
 contrib/completion/git-completion.bash | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 671032bf..2346962d 100755
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -310,8 +310,8 @@ __git_ps1 ()
 				git describe --tags --exact-match HEAD ;;
 			esac 2>/dev/null)" ||
 
-			b="$(cut -c1-7 "$__git_dir/HEAD" 2>/dev/null)..." ||
-			return
+			# detached head abbreviated object name
+			b="${head%${head#???????}}..."
 			b="($b)"
 		fi
 	fi

-- 
1.7.10.1.541.gb1be298
Previous: SZEDER GáborNext: SZEDER Gábor
Message 43 of 50 in “Bash prompt speedup”
  1. 00/19 Bash prompt speedupSZEDER Gábor, May 9, 2012
  2. 01/19 tests: move code to run tests under bash into a helper librarySZEDER Gábor, May 9, 2012
  3. 02/19 tests: add tests for the bash prompt functions in the completion scriptSZEDER Gábor, May 9, 2012
  4. Johannes SixtMay 9, 2012
  5. Junio C HamanoMay 9, 2012
  6. Johannes SixtMay 10, 2012
  7. Junio C HamanoMay 9, 2012
  8. SZEDER GáborMay 9, 2012
  9. 03/19 completion: use __gitdir() in _git_log()SZEDER Gábor, May 9, 2012
  10. Junio C HamanoMay 9, 2012
  11. SZEDER GáborMay 9, 2012
  12. 04/19 completion: respect $GIT_DIRSZEDER Gábor, May 9, 2012
  13. Johannes SixtMay 9, 2012
  14. Junio C HamanoMay 9, 2012
  15. 05/19 bash prompt: don't show the prompt when .git/HEAD is unreadableSZEDER Gábor, May 9, 2012
  16. Junio C HamanoMay 9, 2012
  17. SZEDER GáborMay 9, 2012
  18. 06/19 bash prompt: return early from __git_ps1() when not in a git repositorySZEDER Gábor, May 9, 2012
  19. 07/19 completion: make __gitdir() store repository path in $__git_dirSZEDER Gábor, May 9, 2012
  20. Junio C HamanoMay 9, 2012
  21. 08/19 completion: use $__git_dir instead of $(__gitdir)SZEDER Gábor, May 9, 2012
  22. Junio C HamanoMay 9, 2012
  23. SZEDER GáborMay 9, 2012
  24. Junio C HamanoMay 9, 2012
  25. SZEDER GáborMay 9, 2012
  26. 09/19 completion: platform-specific helper function to get physical pathSZEDER Gábor, May 9, 2012
  27. Johannes SixtMay 9, 2012
  28. 10/19 completion: use bash builtins to search for repositorySZEDER Gábor, May 9, 2012
  29. Junio C HamanoMay 9, 2012
  30. SZEDER GáborMay 9, 2012
  31. Junio C HamanoMay 9, 2012
  32. 11/19 bash prompt: use bash builtins to find out current branchSZEDER Gábor, May 9, 2012
  33. Junio C HamanoMay 9, 2012
  34. SZEDER GáborMay 9, 2012
  35. Junio C HamanoMay 9, 2012
  36. SZEDER GáborMay 9, 2012
  37. Junio C HamanoMay 9, 2012
  38. 12/19 bash prompt: use bash builtins to check whether inside git dirSZEDER Gábor, May 9, 2012
  39. Johannes SixtMay 9, 2012
  40. Junio C HamanoMay 9, 2012
  41. 13/19 bash prompt: check whether inside the worktree only when necessarySZEDER Gábor, May 9, 2012
  42. 14/19 bash prompt: use bash builtins to find out current branch during rebaseSZEDER Gábor, May 9, 2012
  43. 15/19 bash prompt: use bash builtins to get detached HEAD abbrev. object nameSZEDER Gábor, May 9, 2012
  44. 16/19 bash prompt: display stash and upstream state even inside the repositorySZEDER Gábor, May 9, 2012
  45. 17/19 bash prompt: use bash builtins to check stash stateSZEDER Gábor, May 9, 2012
  46. 18/19 bash prompt: avoid command substitution when checking for untracked filesSZEDER Gábor, May 9, 2012
  47. Junio C HamanoMay 9, 2012
  48. 19/19 bash prompt: alternative git prompt without command substitutionSZEDER Gábor, May 9, 2012
  49. Andrew SayersMay 9, 2012
  50. SZEDER GáborMay 9, 2012

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