Add support for a file explorer

[brendan-kellam]

After performing a search and finding a result, it would be useful if we could click into the file and get a "full-screen" preview of the file, along with a file hierarchy on the right. Something similar to GitHub:

[KonradStanski]

Looking into this and investigating existing url templates:

Github:

file:
https://github.com/sourcegraph/zoekt/blob/main/json/json.go
branch:
https://github.com/sourcegraph/zoekt/blob/zoekt-debug/json/json.go
specific commit:
https://github.com/sourcegraph/zoekt/blob/87a0b748f0caf8209e493479bef144d5ef241677/json/json.go
Template:
https://github.com/${org}/${repo}/${blob|tree}/${branch-tag-commit}/${file-path}
Important notes:
When navigating, if the file-path is a file, we use "blob". When it is a folder, we use "tree"

Sourcegraph:

folder:
https://sourcegraph.com/github.com/microsoft/vscode/-/tree/src/vs/workbench/contrib/testing/common
file:
https://sourcegraph.com/github.com/microsoft/vscode/-/blob/src/vs/workbench/contrib/testing/common/observableValue.ts
branch:
https://sourcegraph.com/github.com/microsoft/vscode@line-height/-/blob/src/vs/workbench/contrib/testing/common/observableValue.ts
https://sourcegraph.com/github.com/microsoft/vscode/-/blob/src/vs/workbench/contrib/testing/common/testExplorerFilterState.ts
Template:
https://sourcegraph.com/${code-host}/${org}/${repo}/@${branch-tag-commit}/-/${blob|tree}/${file-path}
Important notes:
branch + "@" is optional, if left out defaults to head.
When navigating, if the file-path is a file, we use "blob". When it is a folder, we use "tree"

Gitlab:

file | folder:
https://${gitlab-host}/${user-org}/${repo}/-/${blob|tree}/${branch-tag-commit}/${file-path}?ref_type=heads
Important notes:
When navigating, if the file-path is a file, we use "blob". When it is a folder, we use "tree"

[KonradStanski]

Some observations:

• Seems like the consensus is put "tree" in the URL path when looking at a folder, and "blob" when looking at file.
• branches, tags, commits are treated as equivalent.
• need some way of including the different code host "repo/project/org/user/ect" paths uniformly. Github paths include an org, whereas gerrit projects can include "/" in the repo name to group them in "folders".
  • Sourcegraph probably handles this the best, as it already encodes all of these hosts.
• should we use query params for some of these?
• It seems like gitlab and sourcegraph delineate the "org/host/repo" preamble from the path with "/~/"
• Need to make sure to handle the case where 2 different code hosts have the same repo name.

[KonradStanski]

Will be good to support "goto def" search and "find references" search when browsing code:
This can work like what sourcegraph uses:
https://sourcegraph.com/docs/code-search/code-navigation/search_based_code_navigation
Perhaps in a codemirror tooltip:
https://codemirror.net/examples/tooltip/