Library update fails with git provider and fixed sync-version

[jfrimmel]

I've noticed a problem when using fixed library versions in conjunction with libraries, that should be updated. This can reproduced with the current master (commit b604f53d):

• create a temporary virtual environment and install the latest fusesoc

  mkdir tmp && cd tmp
  python -m venv .venv
  . .venv/bin/activate
  pip install --force-reinstall git+https://github.com/olofk/fusesoc.git

• reproduce the issue

  $ fusesoc library add https://github.com/fusesoc/fusesoc-generators --sync-version v0.1.3
  INFO: Cloning library into fusesoc_libraries/fusesoc-generators
  <snip>
  INFO: Checkout out fusesoc-generators at version v0.1.3
  $ fusesoc library update
  INFO: fusesoc-generators : Updating...
  INFO: Checkout out fusesoc-generators at version v0.1.3
  You are not currently on a branch.
  Please specify which branch you want to merge with.
  See git-pull(1) for details.
  
      git pull <remote> <branch>
  
  ERROR: fusesoc-generators : Failed to update library: "git -C fusesoc_libraries/fusesoc-generators pull" exited with an error code. See stderr for details.

I think this can be solved rather easily, by replacing git pull with git fetch when a sync-version is requested. I might open a PR for this soon.

[jfrimmel]

The fix is indeed simple:

diff --git a/fusesoc/provider/git.py b/fusesoc/provider/git.py
index cbcf3a1..bb1af4b 100644
--- a/fusesoc/provider/git.py
+++ b/fusesoc/provider/git.py
@@ -38,7 +38,8 @@ class Git(Provider):
 
     @staticmethod
     def update_library(library):
-        git_args = ["-C", library.location, "pull"]
+        download_option = "pull" if not library.sync_version else "fetch"
+        git_args = ["-C", library.location, download_option]
         try:
             Git._checkout_library_version(library)
             Launcher("git", git_args).run()

I need to add a test for it. After that, I'll submit a pull request.