Setting up and using Meld as your git difftool and mergetool

Question

Although much of the information in this question and answer is available on StackOverflow, it is spread out over lots of pages and among other answers which are either wrong or misleading. It took me a while to piece together everything I wanted to know.

There are a lot of different programs that can be used as your git difftool and mergetool, and there is certainly no consensus as to which is the best (opinions, requirements, and OSes will clearly differ).

Meld is a popular free, open-source, and cross-platform (UNIX/Linux, OSX, Windows) choice as shown in the StackOverflow question, What's the best visual merge tool for Git?, in which the answer proposing Meld has more than 3 times the votes as any other tool.

The following 2 questions will be answered in my answer below:

How do I set up and use Meld as my git difftool?
How do I set up and use Meld as my git mergetool?

Note: It is not necessary to use the same program as both your difftool and mergetool, different programs can be set for both.

User · Answer

I prefer to setup meld as a separate command, like so:

git config --global alias.meld '!git difftool -t meld --dir-diff'

This makes it similar to the git-meld.pl script here: https://github.com/wmanley/git-meld

You can then just run

git meld

User · Answer

For Windows  Run these commands in Git Bash   git config --global diff tool meld git config --global difftool meld path  C  Program Files  x86  Meld Meld exe  git config --global difftool prompt false  git config --global merge tool meld git config --global mergetool meld path  C  Program Files  x86  Meld Meld exe  git config --global mergetool prompt false    Update the file path for Meld exe if yours is different    For Linux   Run these commands in Git Bash   git config --global diff tool meld git config --global difftool meld path   usr bin meld  git config --global difftool prompt false  git config --global merge tool meld git config --global mergetool meld path   usr bin meld  git config --global mergetool prompt false   You can verify Meld s path using this command   which meld

User · Answer

This is an answer targeting primarily developers using Windows, as the path syntax of the diff tool differs from other platforms.

I use Kdiff3 as the git mergetool, but to set up the git difftool as Meld, I first installed the latest version of Meld from Meldmerge.org then added the following to my global .gitconfig using:

git config --global -e

Note, if you rather want Sublime Text 3 instead of the default Vim as core ditor, you can add this to the .gitconfig file:

[core]
editor = 'c:/Program Files/Sublime Text 3/sublime_text.exe'

Then you add inn Meld as the difftool

[diff]
tool = meld
guitool = meld 

[difftool "meld"]
cmd = \"C:/Program Files (x86)/Meld/Meld.exe\" \"$LOCAL\" \"$REMOTE\" --label \"DIFF 
(ORIGINAL MY)\"
prompt = false
path = C:\\Program Files (x86)\\Meld\\Meld.exe

Note the leading slash in the cmd above, on Windows it is necessary.

It is also possible to set up an alias to show the current git diff with a --dir-diff option. This will list the changed files inside Meld, which is handy when you have altered multiple files (a very common scenario indeed).

The alias looks like this inside the .gitconfig file, beneath [alias] section:

showchanges = difftool --dir-diff

To show the changes I have made to the code I then just enter the following command:

git showchanges

The following image shows how this --dir-diff option can show a listing of changed files (example):

Then it is possible to click on each file and show the changes inside Meld.

User · Answer

For Windows 10 I had to put this in my  gitconfig    merge    tool   meld  mergetool  meld     cmd    C  Program Files  x86  Meld Meld exe   LOCAL  BASE  REMOTE --output  MERGED  mergetool    prompt   false   Everything else you need to know is written in this super answer by mattst further above   PS  For some reason  this only worked with Meld 3 18 x  Meld 3 20 x gives me an error

User · Answer

How do I set up and use Meld as my git difftool   git difftool displays the diff using a GUI diff program  i e  Meld  instead of displaying the diff output in your terminal    Although you can set the GUI program on the command line using -t  lt tool gt    --tool  lt tool gt  it makes more sense to configure it in your  gitconfig file   Note  See the sections about escaping quotes and Windows paths at the bottom      Add the following to your  gitconfig file   diff      tool   meld  difftool      prompt   false  difftool  meld       cmd   meld   LOCAL    REMOTE     Note  These settings will not alter the behaviour of git diff which will continue to function as usual    You use git difftool in exactly the same way as you use git diff  e g   git difftool  lt COMMIT HASH gt  file name git difftool  lt BRANCH NAME gt  file name git difftool  lt COMMIT HASH 1 gt   lt COMMIT HASH 2 gt  file name   If properly configured a Meld window will open displaying the diff using a GUI interface   The order of the Meld GUI window panes can be controlled by the order of  LOCAL and  REMOTE in cmd  that is to say which file is shown in the left pane and which in the right pane  If you want them the other way around simply swap them around like this       cmd   meld   REMOTE    LOCAL    Finally the prompt   false line simply stops git from prompting you as to whether you want to launch Meld or not  by default git will issue a prompt     How do I set up and use Meld as my git mergetool   git mergetool allows you to use a GUI merge program  i e  Meld  to resolve the merge conflicts that have occurred during a merge   Like difftool you can set the GUI program on the command line using -t  lt tool gt    --tool  lt tool gt  but  as before  it makes more sense to configure it in your  gitconfig file   Note  See the sections about escaping quotes and Windows paths at the bottom      Add the following to your  gitconfig file   merge      tool   meld  mergetool  meld         Choose one of these 2 lines  not both   explained below      cmd   meld   LOCAL    MERGED    REMOTE  --output   MERGED      cmd   meld   LOCAL    BASE    REMOTE  --output   MERGED    You do NOT use git mergetool to perform an actual merge  Before using git mergetool you perform a merge in the usual way with git  e g   git checkout master git merge branch name   If there is a merge conflict git will display something like this     git merge branch name Auto-merging file name CONFLICT  content   Merge conflict in file name Automatic merge failed  fix conflicts and then commit the result    At this point file name will contain the partially merged file with the merge conflict information  that s the file with all the  gt  gt  gt  gt  gt  gt  gt  and  lt  lt  lt  lt  lt  lt  lt  entries in it    Mergetool can now be used to resolve the merge conflicts  You start it very easily with   git mergetool   If properly configured a Meld window will open displaying 3 files  Each file will be contained in a separate pane of its GUI interface   In the example  gitconfig entry above  2 lines are suggested as the  mergetool  meld   cmd line  In fact there are all kinds of ways for advanced users to configure the cmd line  but that is beyond the scope of this answer   This answer has 2 alternative cmd lines which  between them  will cater for most users  and will be a good starting point for advanced users who wish to take the tool to the next level of complexity   Firstly here is what the parameters mean     LOCAL is the file in the current branch  e g  master    REMOTE is the file in the branch being merged  e g  branch name    MERGED is the partially merged file with the merge conflict information in it   BASE is the shared commit ancestor of  LOCAL and  REMOTE  this is to say the file as it was when the branch containing  REMOTE was originally created    I suggest you use either    mergetool  meld       cmd   meld   LOCAL    MERGED    REMOTE  --output   MERGED    or    mergetool  meld       cmd   meld   LOCAL    BASE    REMOTE  --output   MERGED        See  Note On Output File  which explains --output   MERGED     The choice is whether to use  MERGED or  BASE in between  LOCAL and  REMOTE   Either way Meld will display 3 panes with  LOCAL and  REMOTE in the left and right panes and either  MERGED or  BASE in the middle pane   In BOTH cases the middle pane is the file that you should edit to resolve the merge conflicts  The difference is just in which starting edit position you d prefer   MERGED for the file which contains the partially merged file with the merge conflict information or  BASE for the shared commit ancestor of  LOCAL and  REMOTE   Since both cmd lines can be useful I keep them both in my  gitconfig file  Most of the time I use the  MERGED line and the  BASE line is commented out  but the commenting out can be swapped over if I want to use the  BASE line instead    Note On Output File  Do not worry that --output   MERGED  is used in cmd regardless of whether  MERGED or  BASE was used earlier in the cmd line  The --output option simply tells Meld what filename git wants the conflict resolution file to be saved in  Meld will save your conflict edits in that file regardless of whether you use  MERGED or  BASE as your starting edit point   After editing the middle pane to resolve the merge conflicts  just save the file and close the Meld window  Git will do the update automatically and the file in the current branch  e g  master  will now contain whatever you ended up with in the middle pane   git will have made a backup of the partially merged file with the merge conflict information in it by appending  orig to the original filename  e g  file name orig  After checking that you are happy with the merge and running any tests you may wish to do  the  orig file can be deleted   At this point you can now do a commit to commit the changes   If  while you are editing the merge conflicts in Meld  you wish to abandon the use of Meld  then quit Meld without saving the merge resolution file in the middle pane  git will respond with the message file name seems unchanged and then ask Was the merge successful   y n   if you answer n then the merge conflict resolution will be aborted and the file will remain unchanged  Note that if you have saved the file in Meld at any point then you will not receive the warning and prompt from git   Of course you can just delete the file and replace it with the backup  orig file that git made for you    If you have more than 1 file with merge conflicts then git will open a new Meld window for each  one after another until they are all done  They won t all be opened at the same time  but when you finish editing the conflicts in one  and close Meld  git will then open the next one  and so on until all the merge conflicts have been resolved   It would be sensible to create a dummy project to test the use of git mergetool before using it on a live project  Be sure to use a filename containing a space in your test  in case your OS requires you to escape the quotes in the cmd line  see below     Escaping quote characters  Some operating systems may need to have the quotes in cmd escaped  Less experienced users should remember that config command lines should be tested with filenames that include spaces  and if the cmd lines don t work with the filenames that include spaces then try escaping the quotes  e g   cmd   meld    LOCAL      REMOTE     In some cases more complex quote escaping may be needed  The 1st of the Windows path links below contains an example of triple-escaping each quote  It s a bore but sometimes necessary  e g   cmd   meld      LOCAL          REMOTE       Windows paths  Windows users will probably need extra configuration added to the Meld cmd lines  They may need to use the full path to meldc  which is designed to be called on Windows from the command line  or they may need or want to use a wrapper  They should read the StackOverflow pages linked below which are about setting the correct Meld cmd line for Windows  Since I am a Linux user I am unable to test the various Windows cmd lines and have no further information on the subject other than to recommend using my examples with the addition of a full path to Meld or meldc  or adding the Meld program folder to your path    Git Diff and Meld on Windows How to set Meld as git mergetool Git mergetool with Meld on Windows   Ignoring trailing whitespace with Meld  Meld has a number of preferences that can be configured in the GUI   In the preferences Text Filters tab there are several useful filters to ignore things like comments when performing a diff  Although there are filters to ignore All whitespace and Leading whitespace  there is no ignore Trailing whitespace filter  this has been suggested as an addition in the Meld mailing list but is not available in my version    Ignoring trailing whitespace is often very useful  especially when collaborating  and can be manually added easily with a simple regular expression in the Meld preferences Text Filters tab     Use either of these regexes depending on how comprehensive you want it to be     t       t r f v        I hope this helps everyone

User · Answer

It can be complicated to compute a diff in your head from the different sections in $MERGED and apply that. In my setup, meld helps by showing you these diffs visually, using:

[merge]
    tool = mymeld
    conflictstyle = diff3

[mergetool "mymeld"]
    cmd = meld --diff $BASE $REMOTE --diff $REMOTE $LOCAL --diff $LOCAL $MERGED

It looks strange but offers a very convenient work-flow, using three tabs:

in tab 1 you see (from left to right) the change that you should make in tab 2 to solve the merge conflict.
in the right side of tab 2 you apply the "change that you should make" and copy the entire file contents to the clipboard (using ctrl-a and ctrl-c).
in tab 3 replace the right side with the clipboard contents. If everything is correct, you will now see - from left to right - the same change as shown in tab 1 (but with different contexts). Save the changes made in this tab.

Notes:

don't edit anything in tab 1
don't save anything in tab 2 because that will produce annoying popups in tab 3

User · Answer

I follow this simple setup with meld  Meld is free and opensource diff tool  You will see nice side by side comparison of files and directory for any code changes   Install meld in your Linux using yum apt  Add following line in your    gitconfig file    diff      tool   meld    Go to your code repo and type following command to see difference between last committed changes and current working directory  Unstaged uncommited changes    git difftool --dir-diff      To see difference between last committed code and staged code  use following command   git difftool --cached --dir-diff

User · Answer

While the other answer is correct  here s the fastest way to just go ahead and configure Meld as your visual diff tool  Just copy paste this   git config --global diff tool meld git config --global difftool prompt false   Now run git difftool in a directory and Meld will be launched for each different file   Side note  Meld is surprisingly slow at comparing CSV files  and no Linux diff tool I ve found is faster than this Windows tool called Compare It   last updated in 2010

[git] Setting up and using Meld as your git difftool and mergetool

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