suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

git-checkout: faster discovery of commit in common case

Browse Source 
When the desired reference is not an advertised commit, then try
pulling just a few commits --- at depth 8, 16, and 32 -- from the
"master" branch to check whether the commit can be found that way. If
not, fall back to the exhaustive search that requires a full download.

This should help with the common case that a package reference into
the Racket repo is a few commits behind the current master branch
(because the package server hasn't scanned the repo recently enough).
It's much faster to disover that the commit is within the first 32,
which is almost always is, than to download the entire repository.
This commit is contained in:
Matthew Flatt 2019-02-02 11:09:34 -07:00
parent 7ea98c671c
commit 608005ac06
1 changed files with 41 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
racket/collects/net/git-checkout.rkt
View File

@ -51,7 +51,7 @@
#:strict-links? [strict-links? #f]
#:username [username (current-git-username)]
#:password [password (current-git-password)])
(let retry-loop ([given-depth given-depth])
(let retry-loop ([given-depth given-depth] [try-limit-depth (and given-depth 8)] [try-only-master? #t])
(define tmp-dir (or given-tmp-dir
(make-temporary-file "git~a" 'directory)))
(define port (or given-port (case transport
@ -91,7 +91,7 @@
;; Find the commits needed for `ref`:
(define-values (ref-commit ; #f or an ID string
want-commits) ; list of ID string
(select-commits ref refs status))
(select-commits ref refs status try-only-master?))
(unless dest-dir
(write-pkt o) ; clean termination
@ -101,13 +101,15 @@
(or ref-commit ref)))))
(define depth (and given-depth
ref-commit
(or ref-commit try-limit-depth)
(cond
[(member "shallow" server-capabilities)
given-depth]
[else
(status "Server does not support `shallow`")
#f])))
[(member "shallow" server-capabilities)
(if ref-commit
given-depth
try-limit-depth)]
[else
(status "Server does not support `shallow`")
#f])))
(unless dumb-protocol?
;; Tell the server which commits we need
@ -171,8 +173,7 @@
(lambda ()
(esc (lambda ()
(status "Unexpected EOF; retrying without depth")
(retry-loop #f)))))))
(retry-loop #f #f #f)))))))
(maybe-save-objects objs "objs")
;; Convert deltas into full objects withing `tmp`:
@ -182,8 +183,21 @@
(define commit
(or ref-commit
(find-commit-as-reference ref obj-ids)))
(find-commit-as-reference ref obj-ids
(and (or try-only-master?
(and try-limit-depth
(eqv? depth try-limit-depth)))
(lambda ()
(esc (lambda ()
(cond
[(and depth (eqv? depth try-limit-depth)
(try-limit-depth . < . 32))
(status "no matching commit found; trying deeper search")
(retry-loop given-depth (* try-limit-depth 2) try-only-master?)]
[else
(status "no matching commit found; trying broader search")
(retry-loop given-depth #f #f)]))))))))
;; Extract the tree from the packfile objects:
(status "Extracting tree to ~a" dest-dir)
(extract-commit-tree (hex-string->bytes commit)
@ -341,7 +355,7 @@
;; initial response. If we can, the list of requested IDs will be
;; just that one. Otherwise, we'll have to return a list of all
;; IDs, and then we'll look for the reference later.
(define (select-commits ref refs status)
(define (select-commits ref refs status try-only-master?)
(define ref-looks-like-id? (regexp-match? #rx"^[0-9a-f]+$" ref))
(define ref-rx (byte-regexp (bytes-append
@ -366,9 +380,16 @@
(cond
[ref-commit (list ref-commit)]
[ref-looks-like-id?
(status "Requested reference looks like commit id; getting all commits")
(for/list ([ref (in-list refs)])
(cadr ref))]
(cond
[try-only-master?
(status "Requested reference looks like commit id; try within master")
(define-values (master-ref-commit want-commits)
(select-commits "master" refs status #f))
want-commits]
[else
(status "Requested reference looks like commit id; getting all commits")
(for/list ([ref (in-list refs)])
(cadr ref))])]
[else
(raise-git-error 'git "could not find requested reference\n reference: ~a" ref)]))
@ -601,7 +622,7 @@
;; ----------------------------------------
;; Finding a commit id
(define (find-commit-as-reference ref obj-ids)
(define (find-commit-as-reference ref obj-ids fail-not-found)
(define rx (id-ref->regexp ref))
(define matches
(for/list ([(id obj) (in-hash obj-ids)]
@ -611,7 +632,9 @@
(cond
[(= 1 (length matches)) (car matches)]
[(null? matches)
(raise-git-error 'git-checkout "no commit found matching id: ~a" ref)]
(if fail-not-found
(fail-not-found)
(raise-git-error 'git-checkout "no commit found matching id: ~a" ref))]
[else
(raise-git-error 'git-checkout "found multiple commits matching id: ~a" ref)]))