docs: add CLI help

docs/cmd/tk_create_source_git.md

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+## tk create source git
+
+Create or update a git source
+
+### Synopsis
+
+
+The create source command generates a GitRepository resource and waits for it to sync.
+For Git over SSH, host and SSH keys are automatically generated and stored in a Kubernetes secret.
+For private Git repositories, the basic authentication credentials are stored in a Kubernetes secret.
+
+```
+tk create source git [name] [flags]
+```
+
+### Examples
+
+```
+  # Create a source from a public Git repository master branch
+  create source git podinfo \
+    --url=https://github.com/stefanprodan/podinfo \
+    --branch=master
+
+  # Create a source from a Git repository pinned to specific git tag
+  create source git podinfo \
+    --url=https://github.com/stefanprodan/podinfo \
+    --tag="3.2.3"
+
+  # Create a source from a public Git repository tag that matches a semver range
+  create source git podinfo \
+    --url=https://github.com/stefanprodan/podinfo \
+    --tag-semver=">=3.2.0 <3.3.0"
+
+  #  Create a source from a Git repository using SSH authentication
+  create source git podinfo \
+    --url=ssh://git@github.com/stefanprodan/podinfo \
+    --branch=master
+
+  # Create a source from a Git repository using basic authentication
+  create source git podinfo \
+    --url=https://github.com/stefanprodan/podinfo \
+    --username=username \
+    --password=password
+
+```
+
+### Options
+
+```
+      --branch string       git branch (default "master")
+  -h, --help                help for git
+  -p, --password string     basic authentication password
+      --tag string          git tag
+      --tag-semver string   git tag semver range
+      --url string          git address, e.g. ssh://git@host/org/repository
+  -u, --username string     basic authentication username
+```
+
+### Options inherited from parent commands
+
+```
+      --components strings   list of components, accepts comma-separated values (default [source-controller,kustomize-controller])
+      --interval duration    source sync interval (default 1m0s)
+      --kubeconfig string    path to the kubeconfig file (default "~/.kube/config")
+      --namespace string     the namespace scope for this operation (default "gitops-system")
+      --timeout duration     timeout for this operation (default 5m0s)
+      --verbose              print generated objects
+```
+
+### SEE ALSO
+
+* [tk create source](tk_create_source.md)	 - Create source commands
+
+###### Auto generated by spf13/cobra on 30-Apr-2020