[Chapel Merge] Make 'updateGITLOG' work when 'main' is the active

Branch: refs/heads/main
Revision: 52049c8
Author: bradcray
Log Message:

Merge pull request #18368 from bradcray/fix-updategitlog-when-main-active

Make 'updateGITLOG' work when 'main' is the active branch

[trivial, not reviewed, but sorry not to have gotten it right the first time]

In my previous "fix", I forgot that when 'main' is the active branch
in a git repo, it's formatted differently in the 'git branch' output.
This fixes the script to deal with that.

Modified Files:
M util/devel/updateGITLOG

Compare: https://github.com/chapel-lang/chapel/compare/bf4837df2cf2...52049c846bec