git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
* [RFC PATCH] gitk: Activate --find-copies-harder
@ 2021-01-04 19:54 Robert Pollak
  2021-01-06 15:58 ` Laszlo Ersek
  0 siblings, 1 reply; 7+ messages in thread
From: Robert Pollak @ 2021-01-04 19:54 UTC (permalink / raw)
  To: Paul Mackerras; +Cc: Laszlo Ersek, git

Naively forward the diff arguments to make --find-copies-harder work.

Signed-off-by: Robert Pollak <robert.pollak@posteo.net>
---
Dear Paul Mackerras,

This patch is an obviously naive attempt to make gitk observe
--find-copies-harder. I am a gitk user with many small projects, so I am
currently using this patch to get better diffs.

With this, gitk displays the copy in the second commit of my test
repository [1] as desired:

similarity index 100%
copy from a
copy to b


I see the following problems with my patch:

1) It is totally untested with all the other args that are collected in
diffargs, like e.g. "-O<orderfile>", since I didn't need them yet.

2) Even if --find-copies-harder is the only diff argument used, there
might be unintended side effects, since the modified procedure 'diffcmd'
is called in several places. I did not systematically test all these
code paths.


To deal with 1), I could rename the variable 'vdflags' to
'vdflags_ignored' and continue using 'vdflags' only for
--find-copies-harder. Later, other flags could be moved over, after
their harmlessness has been proven. Would this be good?

Ad 2), maybe someone with more code knowledge can tell whether this
a real risk? Also, would it be preferable to add the new flag(s) only to
the arguments of the diffcmd call in 'getblobdiffs'?
(as in:
diff --git a/gitk b/gitk
index 23d9dd1..da6b372 100755
--- a/gitk
+++ b/gitk
@@ -8017,7 +8017,7 @@ proc initblobdiffvars {} {
 proc getblobdiffs {ids} {
     global blobdifffd diffids env
     global treediffs
-    global diffcontext
+    global vdflags diffcontext
     global ignorespace
     global worddiff
     global limitdiffs vfilelimit curview
@@ -8031,7 +8031,7 @@ proc getblobdiffs {ids} {
     if {[package vcompare $git_version "1.6.6"] >= 0} {
         set submodule "--submodule"
     }
-    set cmd [diffcmd $ids "-p $textconv $submodule  -C --cc --no-commit-id -U$diffcontext"]
+    set cmd [diffcmd $ids "$vdflags($curview) -p $textconv $submodule  -C --cc --no-commit-id -U$diffcontext"]
     if {$ignorespace} {
         append cmd " -w"
     }
)
For my test case, this also works.


I'd be happy to prepare an updated patch incorporating your feedback.

Having this functionality in gitk will hopefully make some people stop
crafting their git history for copy detection, like described e.g. in
https://devblogs.microsoft.com/oldnewthing/20190919-00/?p=102904 .

I am CCing Laszlo Ersek, because he expressed interest in a similar
topic a year ago:
'gitk feature requests: (1) "diff.orderFile" and (2) "--function-context"',
https://public-inbox.org/git/d972c1f1-c49a-f644-ab1c-6a3e26c43ee3@redhat.com/
.

-- Robert

[1] My minimal test case:
> git init
> echo "a file" > a
> git add a
> git commit -m "a file"
> cp a b
> git add b
> git commit -m "a copy"


 gitk | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gitk b/gitk
index 23d9dd1..eb6ba9a 100755
--- a/gitk
+++ b/gitk
@@ -7869,7 +7869,7 @@ proc addtocflist {ids} {
 }
  proc diffcmd {ids flags} {
-    global log_showroot nullid nullid2 git_version
+    global log_showroot nullid nullid2 git_version vdflags curview
      set i [lsearch -exact $ids $nullid]
     set j [lsearch -exact $ids $nullid2]
@@ -7909,7 +7909,7 @@ proc diffcmd {ids flags} {
         if {$log_showroot} {
             lappend flags --root
         }
-        set cmd [concat | git diff-tree -r $flags $ids]
+        set cmd [concat | git diff-tree -r $vdflags($curview) $flags $ids]
     }
     return $cmd
 }
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-01-11 21:03 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-04 19:54 [RFC PATCH] gitk: Activate --find-copies-harder Robert Pollak
2021-01-06 15:58 ` Laszlo Ersek
2021-01-10 12:59   ` Robert Pollak
2021-01-11  9:21     ` Laszlo Ersek
2021-01-11 12:33       ` Pratyush Yadav
2021-01-11 16:28         ` Laszlo Ersek
2021-01-11 21:00           ` Junio C Hamano

Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).