Support merge of a branch to its upstream

[svitalsky]

Is your feature request related to a problem? Please describe.
When using Git from a command line, especially for downloading updates for some software I otherwise do not contribute to (that is, my master is always to be fast-forwarded, never divergent), my workflow is:

git fetch
# occasionally—though by no means often—check the fetched commits
git merge

Of course after the first (or optional second) step one could call git rebase with the same effect (again, in the case of no divergence), however I prefer git merge as it offers more information on the amount of changes as well as the names of changed files, whereas rebase only informs about success. For example:

<lazygit> [master] $ git merge                                                     
Updating d159b28dc..143d4760f
Fast-forward                   
 .devcontainer/Dockerfile      |  2 --
 .github/workflows/ci.yml      |  1 +
 .gitignore                    |  1 -
 .vscode/settings.json         |  2 +-  
 Makefile                      |  2 +-
 scripts/golangci-lint-shim.sh |  8 ++++++++                
 scripts/lint.sh               | 12 ------------             
 7 files changed, 11 insertions(+), 17 deletions(-)
 create mode 100755 scripts/golangci-lint-shim.sh
 delete mode 100755 scripts/lint.sh

Lazygit however does not offer merge in this situation, in fact it pretends—or I have been unable to find the correct key—that no merge is possible. That's both wrong and irritating: auxiliary tools shouldn't lie about underlying software.

Describe the solution you'd like
I'd like to have option to merge a branch to its already fetched upstream, displaying the same info as when called from command line.

[stefanhaller]

Of course after the first (or optional second) step one could call git rebase with the same effect (again, in the case of no divergence), however I prefer git merge

The usual way to achieve this is to pull, which is p in lazygit. You decide with the pull.rebase git config whether this does a merge or a rebase.

Lazygit however does not offer merge in this situation, in fact it pretends—or I have been unable to find the correct key—that no merge is possible. That's both wrong and irritating: auxiliary tools shouldn't lie about underlying software.

Lazygit's merge command works by selecting the branch that you want to merge in, and then pressing shift-M. If you select the branch itself, shift-M is disabled, and there's an error message explaining that you can't merge a branch into itself. There's no lying here. Lazygit doesn't have the equivalent of doing a git merge without argument.

If you insist that you want to merge branches the way you describe above, I recommend to configure a custom command:

customCommands:
  - key: <whatever>
    command: git merge --ff-only
    context: global
    description: "Fast-forward merge from upstream"
    output: log

I don't see this as a feature that lazygit needs.

[stefanhaller]

Oh, btw:

however I prefer git merge as it offers more information on the amount of changes as well as the names of changed files

You can turn this on for rebases too, using git config --global rebase.stat true. For some reason this is true by default for merges, but false for rebases.

[svitalsky]

I never use pull, I hate that it does two distinct things at once. And of course it is (almost) always possible to reset back when I don't like the changes fetched during the pull, however I find it way more logical to just fetch and then (usually) merge (or rebase ofc.).

Anyway, thank you for the tip to custom command as well as the config option. I've been using Git for years and years, however I am a newbie when it comes to Lazygit.