Is there a "git pull --dry-run" option in Git?

Question

Is there such a thing as git pull --dry-run to see how stuff will be merged before it messes up my working tree?

Right now I am doing:

git fetch origin && git merge --no-commit --no-ff

I did not see anything in the man page for 'git-pull' related to it.

To clarify, I just need it in an Ant script for deployment to see if there are conflicts when doing git pull, then back off exit out of build, fail deployment and leave that directory tree the same it was before git pull.

Why would there be conflicts? Is your deployment script making local commits and if so why? — CB Bailey, Jun 21 '13 at 08:54
In looking at these responses I think we have overlooked a major difference that distributed source control -- A pull/fetch will grab a whole repository, not just one branch. You must specify individual branches as shown in a couple of answers below. — will, Aug 23 '19 at 02:47
@CBBailey ... When many people are working on many branches (e.g different versions and features) there will often be overlap. Checking before hand makes it easier to plan your merge and later pull request. An equivalent command with SVN is: `svn -q -u`. — will, Aug 23 '19 at 02:56

score 77 · Accepted Answer · edited Dec 31 '17 at 19:39

77

I have always relied on the inherent abilities of Git to get me back if a merge fails.

To estimate how the merge might occur, you can start like you did with:

$ git fetch origin branch  # Fetch changes, but don't merge
$ git diff HEAD..origin/branch # Diff your current head to the fetched commit

... personal judgement of potential merge conflicts ...

$ git merge origin/branch # merge with the fetched commit

If things did not go as planned, look at your reflog and reset back to your desired state:

$ git reflog
...
abc987  HEAD@{0}: merge activity
b58aae8 HEAD@{1}: fetch origin/branch
8f3a362 HEAD@{2}: activity before the fetch
...
$ git reset --hard HEAD{2}

edited Dec 31 '17 at 19:39

Peter Mortensen

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answered Jun 20 '13 at 19:53

rynmrtn

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You can also try this since pulling is somehow similar to merging [http://stackoverflow.com/questions/501407/is-there-a-git-merge-dry-run-option](http://stackoverflow.com/questions/501407/is-there-a-git-merge-dry-run-option) – scireon Jul 20 '16 at 08:13
`fatal: ambiguous argument 'HEAD..origin/branch': unknown revision or path not in the working tree.` – Green May 26 '17 at 16:24
@Green try git reset --hard HEAD@{2} – Alex Shenfield Nov 06 '18 at 10:47
@Green maybe like that: `git diff HEAD..origin/master` – Kuronashi Mar 05 '21 at 09:29

score 41 · Answer 2 · answered Jun 20 '13 at 20:07

41

You will need to fetch first to update your local origin/master

git fetch origin

Then you can do:

git diff --name-only origin/master

Will list the files that have changed.

git diff origin/master directory_foo/file_bar.m

Will list the line by line diff of file directory_foo/file_bar.m.

answered Jun 20 '13 at 20:07

GayleDDS

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Thanks for the tip with the --name-only flag – cw24 Feb 21 '14 at 13:24

score 21 · Answer 3 · answered Jun 20 '13 at 19:50

21

You can get the effect you want by creating a new throw-away branch from your current one and doing the git pull there. If you're unhappy with the results, the original branch is intact.

answered Jun 20 '13 at 19:50

gcbenison

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you mean `git stash`? – WesternGun Jul 20 '17 at 07:48
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No , git stash is entirely different. That puts your local changes elsewhere. – RichieHH Aug 30 '18 at 15:57
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@WesternGun being on the branch You want to copy - `git checkout -b testBranchName` – Jacek Słoma Aug 05 '22 at 07:03

rantoniuk · Answer 4 · 2016-12-08T12:54:13.280

19

# fetch new commits from origin
$ git fetch

# check what are the differences and judge if safe to apply
$ git diff origin/master

# actually merge the fetched commits 
$ git pull

edited Dec 08 '16 at 12:54

answered Dec 08 '16 at 12:22

rantoniuk

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Why the downvote? I did a `git diff this-answer/top-answer` and no significant error is found. Please consider leaving a comment when you commit a downvote: `git commit -m "why would you downvote, blah blah blah"`. – WesternGun Jul 20 '17 at 07:50

score 15 · Answer 5 · answered Jan 22 '21 at 14:14

15

Since v2.27.0 there is a dry-run flag

answered Jan 22 '21 at 14:14

OliverE

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Right! Since 06/01/20 there is a dry-run flag for pull (but not for merge) – Codr Mar 19 '21 at 08:24

score 4 · Answer 6 · answered Jun 21 '13 at 08:44

4

Since pulling implies merging, I'd go with running git merge --abort if your script detects there were any conflicts and merging failed.

answered Jun 21 '13 at 08:44

kostix

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If you were doing this against a remote branch (going a `git fetch origin branch` first) it would be `git merge --abort origin/branch` right? – Nick Devereaux Feb 27 '14 at 23:41

Andy P · Answer 7 · 2019-01-27T10:14:59.080

1

See my answer in this similar question:

How to preview git-pull without doing fetch?

this goes to the ~/.gitconfig file:

[alias]
        diffpull=!git fetch && git diff HEAD..@{u}

edited Jan 27 '19 at 10:14

answered May 14 '18 at 13:00

Andy P

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score 1 · Answer 8 · answered Feb 04 '22 at 21:33

OliverE is spot-on: git pull has a dry-run option, so I recommend git pull --dry-run -v to achieve the OP's purpose -- simple and direct. pull did not always have a dry-run option but in previous (and current) versions of git, fetch did (and does) have a dry-run option. Thus, an alternative approach is to do a git fetch --dry-run -v before you do your pull. Always better to check on an action before executing it, than having to spend time reverting.

score 0 · Answer 9 · answered Aug 12 '21 at 23:09

0

Without pulling:

[ "$(git fetch;git diff | wc -l)" != "0" ] && (
echo there are updates
echo do your stuff here
)

or without touching anything:

[ "$(git pull --dry-run | wc -l)" != "0" ] && (
echo there are updates
echo do your stuff here
)

answered Aug 12 '21 at 23:09

Zibri

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Is there a "git pull --dry-run" option in Git?

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