Keeping credit for my work I joined a new lab a while ago, and am having an issue with keeping the credit for my work. Two instances so far:


I co-authored a series of papers with the professor and a senior graduate student. I was always the first author, and it'd be fair to say that I contributed 95% of the research work and 70% of the writing. Somehow the other student was invited to give several talks on our work at various department seminars. I hadn't known until recently when I accidentally discovered his slides in our shared repository. The problem is that, in his slides, he only put his name, and there was no mention of my name/no credit given to me.
Before joining the lab, I developed a research software, which was quite successful and widely used. When I joined the lab, I transferred the development to the lab, and a graduate student helped me to extend the software a bit. When programming, I always sign my code with my name: (C) 2010-2013 by My Name (Email). Just today, when I looked at the code (publicly shared on github), I discovered that the student had deleted my name from all the files and replaced with his name: (C) 2010-2013 by His Name (Email). He even hadn't joined the development until 2012. If people just look at the code, they would think he were the sole author.


Of course I want to keep the credit for my work. But I don't know what I should do. I feel that there is a culture in the lab that people just don't respect the credit for shared work. I don't want to cause heat in the lab. Both those students have been in the lab for longer than me.
Talks with one name only

Here I think that customs vary between having a long list of authors and a long list of collaborators* and only the speaker spelled out on the title, possibly including a long list of authors on the abstract. 

* e.g. a slide listing the contributions of all the collaborators.

I'd recommend having a look how other people in the department handle this, and then maybe expressing astonishment (semi)publicly because where you came from it was handled differently. I think it is preferable to have a public discussion and the customs/style of the lab developing in some way than to offend everyone just because your previous lab put authors and not the speaker on the front slide.

Related issue: I like to know who tells what about my work. But OTOH, I think it is quite usual that you don't recognize your own work when a collaborator presents it... There are also drawbacks to being spelled out on the first page of a talk.

Only student's name in code

I think this is much clearer. And, as you say the code is in a git repo, it is still easy to sort out things now. 

As a first step, talk to the student privately and request that he rolls back these changes and adds "Contributions by " (ideally a contributions line for each logical step in the development with date and name - but the git messages can do that as well) only where he actually contributed code. Of course, if he is the sole author of new files, those stay "his". 

I'm in a field where software isn't (yet) really a category of publication in the mind of most researchers. However, the usual result of not thinking about that is that there is no statement of authorship nor of a license. In contrast to that, deleting author lines is an active step.
As a second step, I'd explain that deleting the authorship lines from source code is as serious as taking a colleague's manuscript and submitting it under his own name without even mentioning the collaborator. 

As a next level of pressure, you could explain to him that you talk to him privately as you do not want to unneccessarily endanger his graduation: from a legal point of view this is a clear violation of your author's moral rights (not necessarily copyright - although also the terms of the license could have been violated). Violation of author's moral rights is an offense that is extremely relevant for academia and thus may put him onto the fast lane to being thrown out of his programme without graduation.
Which you also should keep in mind if you need to go to your boss with the problem: be careful not to destroy more than absolutely necessary here.

(Always assuming of course that the copyright is actually yours as opposed to your previous employer's. But, if you find out that you just have author's (moral) rights, but not the copyright that is a point that makes it necessary right now to "heal" the legal issues by putting the proper copyright and authorship lines into the code ;-) )