VS Code as Merge and Diff tool

[webtroter]

Hi,

I'm having trouble figuring out how to use VSCode as the merge and diff tool for chezmoi.

I have been able to write this configuration :

merge:
  # Based on https://code.visualstudio.com/docs/editor/command-line#_core-cli-options
  command: code
  args:

    - --wait
    - --merge

    - "{{ .Destination }}"  # Path 1
    - "{{ .Target }}"          # Path 2
    - "{{ .Source }}"         # Base
    - "{{ .Source }}"         # Result/Output
 
  # Destination: /home/webtroter/.zshrc
  # Source: /home/webtroter/.local/share/chezmoi/dot_zshrc
  # Target: /tmp/chezmoi-merge2812438473/.zshrc

diff:
  command: code
  args:
    - --wait
    - --diff
    - "{{ .Destination }}"
    - "{{ .Target }}"

I believe my diff config is OK (since it's pretty simple), but I'm struggling with the merge tool config.

I'm definitely not an advanced user of the vscode merge tool (especially the new three-way merge tool), so help here is appreciated.

Right now, with this config, I'm not sure the merge is working correctly.

[twpayne]

What is the output of:

$ chezmoi merge --debug $TARGET

where $TARGET is the target that you're doing the three-way merge of?

The --debug output will show you exactly how chezmoi is invoking code.

[halostatue]

I think that if you do your configuration as:

merge:
  # Based on https://code.visualstudio.com/docs/editor/command-line#_core-cli-options
  command: code
  args:
    - --wait
    - --merge
    - "{{ .Destination }}"  # Path 1
    - "{{ .Source }}"         # Path 2
    - "{{ .Target }}"          # Base
    - "{{ .Source }}"         # Result/Output

It should start working. The main thing that I see is that merge mode in VS Code requires four parameters instead of the typical three.

[webtroter]

Thank you for your reply

I think that if you do your configuration as:

merge:
  # Based on https://code.visualstudio.com/docs/editor/command-line#_core-cli-options
  command: code
  args:
    - --wait
    - --merge
    - "{{ .Destination }}"  # Path 1
    - "{{ .Source }}"         # Path 2
    - "{{ .Target }}"          # Base
    - "{{ .Source }}"         # Result/Output

It should start working. The main thing that I see is that merge mode in VS Code requires four parameters instead of the typical three.

Is it working on your side? Because it makes my VSCode hang when I use that configuration.

[halostatue]

I’m sorry, I had not tested it because while I have VS Code installed, I have never used it for merge completion. My comment was based on reading the documentation bits. By default, merge calls are made with [ "{{ .Destination }}", "{{ .Source }}", "{{ .Target }}" ], which is sufficient for using Vim in a merge mode, and I suspect Emacs. It’s the fourth parameter that is making no sense to me for VS Code.

[webtroter]

From what I read, the fourth parameter should be a common ancestor of both modified version, since vscode does three way merge.

[halostatue]

That’s the third parameter in most implementations. As far as I can tell, {{ .Target }} is the common ancestor. It’s the result/output value which makes no sense to me.

[Startouf]

Have you found the correct way to write it ? I'm not entirely sure why, but VS Code does not open the 3-way merge window, but just opens 3 different files.

[twpayne]

What command do you use to open up a 3-way merge in VS Code when not using chezmoi?

[LegendTheo]

VS codes merge tool was built to work with GIT, looking at the GIT mergetool documentation it provides 4 file paths to the tool:

- $BASE, the common base for both files (in this case I believe is consistent with Target)
- $LOCAL, the file with changes from the local branch (consistent with Source I think)
- $REMOTE, the changes to be merged (Consistent with Destination I think)
- $MERGED, The file where the result should be written (Not sure this exists in chezmoi)?

The issue is that if you pass Source for both either $LOCAL or $BASE code can't update the merge correctly because it's saving to a file that's already open.

I don't know what's normal for 3 way merges, but I don't think what GIT provides is all that out there. Seems like this could be resolved by creating a temp file that has the contents of Source, and providing that as the second file. Then Source could be used as the location to write to.

mergetool doc

relevant paragrah/s:

Instead of running one of the known merge tool programs, git mergetool can be customized to run an alternative program by specifying the command line to invoke in a configuration variable mergetool..cmd.

When git mergetool is invoked with this tool (either through the -t or --tool option or the merge.tool configuration variable) the configured command line will be invoked with $BASE set to the name of a temporary file containing the common base for the merge, if available; $LOCAL set to the name of a temporary file containing the contents of the file on the current branch; $REMOTE set to the name of a temporary file containing the contents of the file to be merged, and $MERGED set to the name of the file to which the merge tool should write the result of the merge resolution.

If the custom merge tool correctly indicates the success of a merge resolution with its exit code, then the configuration variable mergetool..trustExitCode can be set to true. Otherwise, git mergetool will prompt the user to indicate the success of the resolution after the custom tool has exited.

[fluxium]

Here was the approach that worked for me given the following context:

• Windows 10
• pwsh 7.3.9
• git 2.42.0
• chezmoi 2.40.4

Important

My goal was to integrate dotfile differences from a second device into chezmoi. The direction of the merge I used may not be appropriate for your use case.

Goal

Selectively merge hunks from .Destination into .Source before running chezmoi update for the first time on an alternate device I use daily.

Challenges

• code --merge seems to expect 4 distinct file handles to trigger the visual merge UI.
  • As well as to not hang the vscode runtime → VS Code as Merge and Diff tool #2424 (reply in thread)
• chezmoi is providing us with 3 paths.

Behavior

On Windows, chezmoi merge ~\my_config.yml seems to perform the following actions relevant to my goal:

1. Sets .Destination = absolute path of ~\my_config.yml
2. Sets .Source = absolute path of corresponding file in chezmoi repo
3. Creates a dir in ~\AppData\Local\Temp
4. Writes a copy of the file at .Source to previously created dir in Temp
5. Sets .Target = absolute path of file copied to dir in Temp
6. Runs our command

Solution

Since the chezmoi variable merge.command is used to get an exe from PATH, we can use templating to assemble a command that can be argged to a shell.

Note

As @anthonyjclark discovered this can easily be altered to work with other shells. Based on @anthonyjclark's feedback, this solution was altered to leverage bash-like && operator available in PowerShell 7 in case the copy goes sideways.

.chezmoi.toml.tmpl fragment:

[merge]
    command = "pwsh"
    args = ["-Command", "cp {{ `{{ .Target }}` }} {{ `{{ .Target }}` }}.base && code --wait --new-window --merge {{ `{{ .Destination }}` }} {{ `{{ .Target  }}` }} {{ `{{ .Target }}` }}.base {{ `{{ .Source }}` }}"]

So we have 4 file handles to work with, we make a copy of the file chezmoi places at .Target and append the suffix .base.
After the && we assemble the vscode command similarly to the other answers here. The notable exception being the order the paths are provided to code:

• Compare my existing config at .Destination to the file chezmoi placed in the temp dir at .Target.
  • This is equivalent to using .Source as the second path arg, since the file contents will be the same, but leaves .Source available for writing as merge result target.
• The copy we made of the file chezmoi placed in the temp dir and suffixed with .base is provided as the merge base file for no other reason than to make vscode activate the visual merge UI when the window opens.
• Finally, .Source is provided to the last path arg as the merge result target.

After completing the merge in the vscode UI, the file in the chezmoi repo should be ready for commit and/or chezmoi apply/chezmoi update.

[ElanHasson]

sorry, chezmoi edit-config brought up my rendered templated yaml file. I use .chezmoi.yaml.tmpl

[twpayne]

Good idea. #3314 adds a chezmoi edit-config-template command.

[fluxium]

@anthonyjclark @ElanHasson Thanks to you both! I was so used to PowerShell 5 patterns that I didn't realize PowerShell 7 added the && and || operators. I am going to make that refactor. Also, thanks for confirming this can work cross-platform with some minor tweaks.

[stromseng]

This almost worked for me. I wanted to use it directly in my chezmoi.toml file, instead of in a template. Therefore i converted it into the following

[diff]
command = "code"
args = ["--wait", "--diff", "{{ .Destination }}", "{{ .Target }}"]

[merge]
command = "bash"
args = [
    "-c",
    "cp {{ .Target }} {{ .Target }}.base && code --new-window --wait --merge {{ .Destination }} {{ .Target }} {{ .Target }}.base {{ .Source }}",
]

[owpac]

Hello, just wanted to add a working example for chezmoi.yaml.tmpl file:

diff:
  command: "code"
  args:
    - "--wait"
    - "--diff"
    - "{{ `{{ .Destination }}` }}"
    - "{{ `{{ .Target }}` }}"

merge:
  command: "bash"
  args:
    - "-c"
    - "cp {{ `{{ .Target }}` }} {{ `{{ .Target }}` }}.base && code --wait --new-window --merge {{ `{{ .Destination }}` }} {{ `{{ .Target  }}` }} {{ `{{ .Target }}` }}.base {{ `{{ .Source }}` }}"

Also, note that for the diff command, Destination and Target parameters aren't needed (it's working without, at least).