Subject: [PATCH v2 0/1] unpack-trees: exit check_updates() early if updates are not wanted

From: "Elijah Newren via GitGitGadget" <[email-masked]>
Date: Tue, 07 Jan 2020 06:57:56 +0000

In trying to understand check_updates(), I found I was able to simplify the
function by making it exit early when updates are not wanted.

Changes since v1:

 * Added two bullet points to the end of the commit message to explain the
   questions Junio brought up about function calls that are skipped by the
   early return.

Elijah Newren (1):
  unpack-trees: exit check_updates() early if updates are not wanted

 unpack-trees.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

base-commit: 8679ef24ed64018bb62170c43ce73e0261c0600a
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-686%2Fnewren%2Fsimplify-check-updates-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-686/newren/simplify-check-updates-v2
Pull-Request: https://github.com/git/git/pull/686

Range-diff vs v1:

 1:  de0f381284 ! 1:  dd27727332 unpack-trees: exit check_updates() early if updates are not wanted
     @@ -33,6 +33,21 @@
              These two calls to git_attr_set_direction() cancel each other out
              and thus can be omitted when o->dry_run is true just as they
              already are when !o->update.
     +      * The code would previously call setup_collided_checkout_detection()
     +        and report_collided_checkout() even when o->dry_run.  However, this
     +        was just an expensive no-op because
     +        setup_collided_checkout_detection() merely cleared the CE_MATCHED
     +        flag for each cache entry, and report_collided_checkout() reported
     +        which ones had it set.  Since a dry-run would skip all the
     +        checkout_entry() calls, CE_MATCHED would never get set and thus
     +        no collisions would be reported.  Since we can't detect the
     +        collisions anyway without doing updates, skipping the collisions
     +        detection setup and reporting is an optimization.
     +      * The code previously would call get_progress() and
     +        display_progress() even when (!o->update || o->dry_run).  This
     +        served to show how long it took to skip all the updates, which is
     +        somewhat useless.  Since we are skipping the updates, we can skip
     +        showing how long it takes to skip them.
      
          Signed-off-by: Elijah Newren <[email-masked]>

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