generate-cmdlist.sh: spawn fewer processes

The function get_categories() is invoked in a loop over all commands.
As it runs several processes, this takes an awful lot of time on
Windows. To reduce the number of processes, move the process that
filters empty lines to the other invoker of the function, where it is
needed. The invocation of get_categories() in the loop does not need
the empty line filtered away because the result is word-split by the
shell, which eliminates the empty line automatically.

Furthermore, use sort -u instead of sort | uniq to remove yet another
process.

[Ævar: on Linux this seems to speed things up a bit, although with
hyperfine(1) the results are fuzzy enough to land within the
confidence interval]:

$ git show HEAD~:generate-cmdlist.sh >generate-cmdlist.sh.old
$ hyperfine --warmup 1 -L s ,.old -p 'make clean' 'sh generate-cmdlist.sh{s} command-list.txt'
Benchmark #1: sh generate-cmdlist.sh command-list.txt
  Time (mean ± σ):     371.3 ms ±  64.2 ms    [User: 430.4 ms, System: 72.5 ms]
  Range (min … max):   320.5 ms … 517.7 ms    10 runs

Benchmark #2: sh generate-cmdlist.sh.old command-list.txt
  Time (mean ± σ):     489.9 ms ± 185.4 ms    [User: 724.7 ms, System: 141.3 ms]
  Range (min … max):   346.0 ms … 885.3 ms    10 runs

Summary
  'sh generate-cmdlist.sh command-list.txt' ran
    1.32 ± 0.55 times faster than 'sh generate-cmdlist.sh.old command-list.txt'

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/generate-cmdlist.sh b/generate-cmdlist.sh
index 5114f46680ab172e946887ae223bcb4ff51cb1ab..27367915611a08718c00b4fb9f46784a24c37127 100755 (executable)
--- a/generate-cmdlist.sh
+++ b/generate-cmdlist.sh
@@ -11,15 +11,14 @@ command_list () {
 
 get_categories () {
        tr ' ' '\012' |
-       grep -v '^$' |
-       sort |
-       uniq
+       LC_ALL=C sort -u
 }
 
 category_list () {
        command_list "$1" |
        cut -c 40- |
-       get_categories
+       get_categories |
+       grep -v '^$'
 }
 
 get_synopsis () {