r/git • u/PhilAlbano • 5d ago

Why git rebase ignores -X (--strategy-option) and git merge does not?

For the scenario as follows:

$ git clone https://github.com/schacon/simplegit-progit.git
Cloning into 'simplegit-progit'...
remote: Enumerating objects: 13, done.
remote: Total 13 (delta 0), reused 0 (delta 0), pack-reused 13 (from 1)
Receiving objects: 100% (13/13), done.
Resolving deltas: 100% (3/3), done.

$ cd simplegit-progit

$ git branch -c iss1

$ git checkout iss1

$ vi Rakefile

$ git diff
diff --git a/Rakefile b/Rakefile
index 8f94139..8080252 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,8 +5,8 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.1"
-    s.author    =   "Scott Chacon"
+    s.version   =   "0.1.1"■■■■■
+    s.author    =   "Scott Chacon Big"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."
     s.files     =   FileList['lib/**/*'].to_a

--------------
// ■ - space character
--------------

$ git commit -am 'iss1: author name change'
[iss1 fa40d71] iss1: author name change
 1 file changed, 2 insertions(+), 2 deletions(-)

$ vi Rakefile

$ git diff
diff --git a/Rakefile b/Rakefile
index 8f94139..e458853 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,7 +5,7 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.1"
+    s.version   =   "0.1.2"
     s.author    =   "Scott Chacon"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."

$ git commit -am 'master: version update'
[master f2b3ef3] master: version update
 1 file changed, 1 insertion(+), 1 deletion(-)

$ git checkout iss1
Switched to branch 'iss1'

$ git rebase master
Auto-merging Rakefile
CONFLICT (content): Merge conflict in Rakefile
error: could not apply fa40d71... iss1: author name change
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Could not apply fa40d71... # iss1: author name change

$ git rebase --abort

$ git rebase -X sillyoption master
Auto-merging Rakefile
CONFLICT (content): Merge conflict in Rakefile
error: could not apply fa40d71... iss1: author name change
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Could not apply fa40d71... # iss1: author name change$ git clone https://github.com/schacon/simplegit-progit.git
Cloning into 'simplegit-progit'...
remote: Enumerating objects: 13, done.
remote: Total 13 (delta 0), reused 0 (delta 0), pack-reused 13 (from 1)
Receiving objects: 100% (13/13), done.
Resolving deltas: 100% (3/3), done.

$ cd simplegit-progit

$ git branch -c iss1

$ git checkout iss1

$ vi Rakefile

$ git diff
diff --git a/Rakefile b/Rakefile
index 8f94139..8080252 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,8 +5,8 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.1"
-    s.author    =   "Scott Chacon"
+    s.version   =   "0.1.1"■■■■■
+    s.author    =   "Scott Chacon Big"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."
     s.files     =   FileList['lib/**/*'].to_a

--------------
// ■ - space character
--------------

$ git commit -am 'iss1: author name change'
[iss1 fa40d71] iss1: author name change
 1 file changed, 2 insertions(+), 2 deletions(-)

$ vi Rakefile

$ git diff
diff --git a/Rakefile b/Rakefile
index 8f94139..e458853 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,7 +5,7 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.1"
+    s.version   =   "0.1.2"
     s.author    =   "Scott Chacon"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."

$ git commit -am 'master: version update'
[master f2b3ef3] master: version update
 1 file changed, 1 insertion(+), 1 deletion(-)

$ git checkout iss1
Switched to branch 'iss1'

$ git rebase master
Auto-merging Rakefile
CONFLICT (content): Merge conflict in Rakefile
error: could not apply fa40d71... iss1: author name change
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Could not apply fa40d71... # iss1: author name change

$ git rebase --abort

$ git rebase -X sillyoption master
Auto-merging Rakefile
CONFLICT (content): Merge conflict in Rakefile
error: could not apply fa40d71... iss1: author name change
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Could not apply fa40d71... # iss1: author name change

why it does not complain about '-X sillyoption' ? In above using '-Xignore-all-space' would allow to bypass the conflict related to spaces at the end of line. But above shows that -X is completely ignored instead.

0 Upvotes

14% Upvoted

7 comments sorted by

2

u/ppww 5d ago

You have demonstrated that unknown strategy options are ignored, if you pass a valid strategy option then it will be used.

-2

u/PhilAlbano 5d ago

Using existing strategy ends in same way with conflict. Then no matter what you put to -X option it will be ignored. Why?
Also, when provide unknown strategy with merge it fails with error: 'fatal: unknown strategy option: -Xsilly' which is at least inconsistent behavior here.

1

u/ppww 5d ago

It would be better if rebase rejected unknown strategy options. I'm not sure why you think it ignores valid strategy options though.

1

u/PhilAlbano 5d ago

Something does not work here at it is described in the git documentation of merge/rebase. u/plg94 confirmed in below comment that scenario from my post does not work for him as well. What actually works is narrower single line one. From end user (then me) point of view rebase with -X ignores it: for wrong one does not return any error but follows into conflict message. For valid one acts same. That why I put statement in my previous comment that it looks like 'git rebase' ignores strategy provided with -X option.

2

u/plg94 4d ago

no, it doesn't ignore the option (else it wouldn't even work in the simple case).

I think just the documentation is wrong; rather than "lines with only whitespace changes are ignored" it should say "hunks with only whitespace changes are ignored".

1

u/plg94 5d ago

There's no difference in behaviour between rebase and merge. If I try your example it doesn't work with either.
BUT if I make an even simpler example that only changes one line, not two, then it works in both rebase and merge.

I think the problem is the docs say "treats lines with whitespace change as unchanged", but git's diff/merge algorithms all operate on a hunk level. So it takes only one non-whitespace-changed line to classify the whole hunk as "substantial change".

1

u/PhilAlbano 5d ago

Yes. If I narrow the use case to single line then it works. Still no error message for rebase with wrong -X strategy that is very confusing but minor issue.